ssl_test_lib: fix compilation flags for default config

Signed-off-by: Przemek Stekiel <przemyslaw.stekiel@mobica.com>
diff --git a/programs/ssl/ssl_test_lib.c b/programs/ssl/ssl_test_lib.c
index c0704d0..7eebebb 100644
--- a/programs/ssl/ssl_test_lib.c
+++ b/programs/ssl/ssl_test_lib.c
@@ -221,6 +221,7 @@
     return 0;
 }
 
+#if defined(MBEDTLS_USE_PSA_CRYPTO)
 int key_opaque_set_alg_usage( const char *alg1, const char *alg2,
                               psa_algorithm_t *psa_alg1,
                               psa_algorithm_t *psa_alg2,
@@ -284,6 +285,7 @@
 
     return 0;
 }
+#endif /* MBEDTLS_USE_PSA_CRYPTO */
 
 #if defined(MBEDTLS_X509_TRUSTED_CERTIFICATE_CALLBACK)
 int ca_callback( void *data, mbedtls_x509_crt const *child,