Fix build flags for opaque/raw psk checks

Signed-off-by: Przemek Stekiel <przemyslaw.stekiel@mobica.com>
diff --git a/library/ssl_tls12_client.c b/library/ssl_tls12_client.c
index f6a21cb..d286764 100644
--- a/library/ssl_tls12_client.c
+++ b/library/ssl_tls12_client.c
@@ -73,7 +73,9 @@
     return( 0 );
 }
 
-#if defined(MBEDTLS_USE_PSA_CRYPTO)
+#if defined(MBEDTLS_USE_PSA_CRYPTO) && \
+    ( defined(MBEDTLS_KEY_EXCHANGE_ECDHE_PSK_ENABLED ) || \
+      defined(MBEDTLS_KEY_EXCHANGE_PSK_ENABLED) )
 static int ssl_conf_has_static_raw_psk( mbedtls_ssl_config const *conf )
 {
     if( conf->psk_identity     == NULL ||
@@ -87,7 +89,9 @@
 
     return( 0 );
 }
-#endif /* MBEDTLS_USE_PSA_CRYPTO */
+#endif /* MBEDTLS_USE_PSA_CRYPTO &&
+          ( MBEDTLS_KEY_EXCHANGE_ECDHE_PSK_ENABLED ||
+            MBEDTLS_KEY_EXCHANGE_PSK_ENABLED ) */
 
 #endif /* MBEDTLS_KEY_EXCHANGE_SOME_PSK_ENABLED */