Use correct conditionals in programs/ssl (fix unused-function errors)

Signed-off-by: Michael Schuster <michael@schuster.ms>
diff --git a/programs/ssl/ssl_test_common_source.c b/programs/ssl/ssl_test_common_source.c
index ab41a0b..6d333e8 100644
--- a/programs/ssl/ssl_test_common_source.c
+++ b/programs/ssl/ssl_test_common_source.c
@@ -352,6 +352,7 @@
 }
 #endif /* MBEDTLS_X509_CRT_PARSE_C */
 
+#if defined(MBEDTLS_SSL_HANDSHAKE_WITH_CERT_ENABLED)
 static void mbedtls_print_supported_sig_algs(void)
 {
     mbedtls_printf("supported signature algorithms:\n");
@@ -373,3 +374,4 @@
     mbedtls_printf("ecdsa_sha1\n");
     mbedtls_printf("\n");
 }
+#endif /* MBEDTLS_SSL_HANDSHAKE_WITH_CERT_ENABLED */