Fix undeclared dependency on FS_IO in test code

Found by 'all.sh test_no_platform' and by 'tests/scripts/test-ref-configs.pl'.
diff --git a/tests/suites/test_suite_ssl.data b/tests/suites/test_suite_ssl.data
index 4041de2..a3e640b 100644
--- a/tests/suites/test_suite_ssl.data
+++ b/tests/suites/test_suite_ssl.data
@@ -8765,15 +8765,15 @@
 ssl_serialise_session_save_load:1023:""
 
 Session serialisation, save-load: no ticket, cert
-depends_on:MBEDTLS_X509_USE_C:MBEDTLS_PEM_PARSE_C:MBEDTLS_ECDSA_C:MBEDTLS_ECP_DP_SECP256R1_ENABLED:MBEDTLS_SHA256_C
+depends_on:MBEDTLS_X509_USE_C:MBEDTLS_PEM_PARSE_C:MBEDTLS_ECDSA_C:MBEDTLS_ECP_DP_SECP256R1_ENABLED:MBEDTLS_SHA256_C:MBEDTLS_FS_IO
 ssl_serialise_session_save_load:0:"data_files/server5.crt"
 
 Session serialisation, save-load: small ticket, cert
-depends_on:MBEDTLS_SSL_SESSION_TICKETS:MBEDTLS_SSL_CLI_C:MBEDTLS_X509_USE_C:MBEDTLS_PEM_PARSE_C:MBEDTLS_ECDSA_C:MBEDTLS_ECP_DP_SECP256R1_ENABLED:MBEDTLS_SHA256_C
+depends_on:MBEDTLS_SSL_SESSION_TICKETS:MBEDTLS_SSL_CLI_C:MBEDTLS_X509_USE_C:MBEDTLS_PEM_PARSE_C:MBEDTLS_ECDSA_C:MBEDTLS_ECP_DP_SECP256R1_ENABLED:MBEDTLS_SHA256_C:MBEDTLS_FS_IO
 ssl_serialise_session_save_load:42:"data_files/server5.crt"
 
 Session serialisation, save-load: large ticket, cert
-depends_on:MBEDTLS_SSL_SESSION_TICKETS:MBEDTLS_SSL_CLI_C:MBEDTLS_X509_USE_C:MBEDTLS_PEM_PARSE_C:MBEDTLS_ECDSA_C:MBEDTLS_ECP_DP_SECP256R1_ENABLED:MBEDTLS_SHA256_C
+depends_on:MBEDTLS_SSL_SESSION_TICKETS:MBEDTLS_SSL_CLI_C:MBEDTLS_X509_USE_C:MBEDTLS_PEM_PARSE_C:MBEDTLS_ECDSA_C:MBEDTLS_ECP_DP_SECP256R1_ENABLED:MBEDTLS_SHA256_C:MBEDTLS_FS_IO
 ssl_serialise_session_save_load:1023:"data_files/server5.crt"
 
 Session serialisation, load-save: no ticket, no cert
@@ -8788,15 +8788,15 @@
 ssl_serialise_session_load_save:1023:""
 
 Session serialisation, load-save: no ticket, cert
-depends_on:MBEDTLS_X509_USE_C:MBEDTLS_PEM_PARSE_C:MBEDTLS_ECDSA_C:MBEDTLS_ECP_DP_SECP256R1_ENABLED:MBEDTLS_SHA256_C
+depends_on:MBEDTLS_X509_USE_C:MBEDTLS_PEM_PARSE_C:MBEDTLS_ECDSA_C:MBEDTLS_ECP_DP_SECP256R1_ENABLED:MBEDTLS_SHA256_C:MBEDTLS_FS_IO
 ssl_serialise_session_load_save:0:"data_files/server5.crt"
 
 Session serialisation, load-save: small ticket, cert
-depends_on:MBEDTLS_SSL_SESSION_TICKETS:MBEDTLS_SSL_CLI_C:MBEDTLS_X509_USE_C:MBEDTLS_PEM_PARSE_C:MBEDTLS_ECDSA_C:MBEDTLS_ECP_DP_SECP256R1_ENABLED:MBEDTLS_SHA256_C
+depends_on:MBEDTLS_SSL_SESSION_TICKETS:MBEDTLS_SSL_CLI_C:MBEDTLS_X509_USE_C:MBEDTLS_PEM_PARSE_C:MBEDTLS_ECDSA_C:MBEDTLS_ECP_DP_SECP256R1_ENABLED:MBEDTLS_SHA256_C:MBEDTLS_FS_IO
 ssl_serialise_session_load_save:42:"data_files/server5.crt"
 
 Session serialisation, load-save: large ticket, cert
-depends_on:MBEDTLS_SSL_SESSION_TICKETS:MBEDTLS_SSL_CLI_C:MBEDTLS_X509_USE_C:MBEDTLS_PEM_PARSE_C:MBEDTLS_ECDSA_C:MBEDTLS_ECP_DP_SECP256R1_ENABLED:MBEDTLS_SHA256_C
+depends_on:MBEDTLS_SSL_SESSION_TICKETS:MBEDTLS_SSL_CLI_C:MBEDTLS_X509_USE_C:MBEDTLS_PEM_PARSE_C:MBEDTLS_ECDSA_C:MBEDTLS_ECP_DP_SECP256R1_ENABLED:MBEDTLS_SHA256_C:MBEDTLS_FS_IO
 ssl_serialise_session_load_save:1023:"data_files/server5.crt"
 
 Session serialisation, save buffer size: no ticket, no cert
@@ -8811,15 +8811,15 @@
 ssl_serialise_session_save_buf_size:1023:""
 
 Session serialisation, save buffer size: no ticket, cert
-depends_on:MBEDTLS_X509_USE_C:MBEDTLS_PEM_PARSE_C:MBEDTLS_ECDSA_C:MBEDTLS_ECP_DP_SECP256R1_ENABLED:MBEDTLS_SHA256_C
+depends_on:MBEDTLS_X509_USE_C:MBEDTLS_PEM_PARSE_C:MBEDTLS_ECDSA_C:MBEDTLS_ECP_DP_SECP256R1_ENABLED:MBEDTLS_SHA256_C:MBEDTLS_FS_IO
 ssl_serialise_session_save_buf_size:0:"data_files/server5.crt"
 
 Session serialisation, save buffer size: small ticket, cert
-depends_on:MBEDTLS_SSL_SESSION_TICKETS:MBEDTLS_SSL_CLI_C:MBEDTLS_X509_USE_C:MBEDTLS_PEM_PARSE_C:MBEDTLS_ECDSA_C:MBEDTLS_ECP_DP_SECP256R1_ENABLED:MBEDTLS_SHA256_C
+depends_on:MBEDTLS_SSL_SESSION_TICKETS:MBEDTLS_SSL_CLI_C:MBEDTLS_X509_USE_C:MBEDTLS_PEM_PARSE_C:MBEDTLS_ECDSA_C:MBEDTLS_ECP_DP_SECP256R1_ENABLED:MBEDTLS_SHA256_C:MBEDTLS_FS_IO
 ssl_serialise_session_save_buf_size:42:"data_files/server5.crt"
 
 Session serialisation, save buffer size: large ticket, cert
-depends_on:MBEDTLS_SSL_SESSION_TICKETS:MBEDTLS_SSL_CLI_C:MBEDTLS_X509_USE_C:MBEDTLS_PEM_PARSE_C:MBEDTLS_ECDSA_C:MBEDTLS_ECP_DP_SECP256R1_ENABLED:MBEDTLS_SHA256_C
+depends_on:MBEDTLS_SSL_SESSION_TICKETS:MBEDTLS_SSL_CLI_C:MBEDTLS_X509_USE_C:MBEDTLS_PEM_PARSE_C:MBEDTLS_ECDSA_C:MBEDTLS_ECP_DP_SECP256R1_ENABLED:MBEDTLS_SHA256_C:MBEDTLS_FS_IO
 ssl_serialise_session_save_buf_size:1023:"data_files/server5.crt"
 
 Session serialisation, load buffer size: no ticket, no cert
@@ -8834,13 +8834,13 @@
 ssl_serialise_session_load_buf_size:1023:""
 
 Session serialisation, load buffer size: no ticket, cert
-depends_on:MBEDTLS_X509_USE_C:MBEDTLS_PEM_PARSE_C:MBEDTLS_ECDSA_C:MBEDTLS_ECP_DP_SECP256R1_ENABLED:MBEDTLS_SHA256_C
+depends_on:MBEDTLS_X509_USE_C:MBEDTLS_PEM_PARSE_C:MBEDTLS_ECDSA_C:MBEDTLS_ECP_DP_SECP256R1_ENABLED:MBEDTLS_SHA256_C:MBEDTLS_FS_IO
 ssl_serialise_session_load_buf_size:0:"data_files/server5.crt"
 
 Session serialisation, load buffer size: small ticket, cert
-depends_on:MBEDTLS_SSL_SESSION_TICKETS:MBEDTLS_SSL_CLI_C:MBEDTLS_X509_USE_C:MBEDTLS_PEM_PARSE_C:MBEDTLS_ECDSA_C:MBEDTLS_ECP_DP_SECP256R1_ENABLED:MBEDTLS_SHA256_C
+depends_on:MBEDTLS_SSL_SESSION_TICKETS:MBEDTLS_SSL_CLI_C:MBEDTLS_X509_USE_C:MBEDTLS_PEM_PARSE_C:MBEDTLS_ECDSA_C:MBEDTLS_ECP_DP_SECP256R1_ENABLED:MBEDTLS_SHA256_C:MBEDTLS_FS_IO
 ssl_serialise_session_load_buf_size:42:"data_files/server5.crt"
 
 Session serialisation, load buffer size: large ticket, cert
-depends_on:MBEDTLS_SSL_SESSION_TICKETS:MBEDTLS_SSL_CLI_C:MBEDTLS_X509_USE_C:MBEDTLS_PEM_PARSE_C:MBEDTLS_ECDSA_C:MBEDTLS_ECP_DP_SECP256R1_ENABLED:MBEDTLS_SHA256_C
+depends_on:MBEDTLS_SSL_SESSION_TICKETS:MBEDTLS_SSL_CLI_C:MBEDTLS_X509_USE_C:MBEDTLS_PEM_PARSE_C:MBEDTLS_ECDSA_C:MBEDTLS_ECP_DP_SECP256R1_ENABLED:MBEDTLS_SHA256_C:MBEDTLS_FS_IO
 ssl_serialise_session_load_buf_size:1023:"data_files/server5.crt"
diff --git a/tests/suites/test_suite_ssl.function b/tests/suites/test_suite_ssl.function
index f172e1e..2b755ed 100644
--- a/tests/suites/test_suite_ssl.function
+++ b/tests/suites/test_suite_ssl.function
@@ -284,7 +284,7 @@
     memset( session->id, 66, session->id_len );
     memset( session->master, 17, sizeof( session->master ) );
 
-#if defined(MBEDTLS_X509_CRT_PARSE_C)
+#if defined(MBEDTLS_X509_CRT_PARSE_C) && defined(MBEDTLS_FS_IO)
     if( strlen( crt_file ) != 0 )
     {
         int ret;