config_psa: do not update legacy symbols in client-only PSA build

Signed-off-by: Valerio Setti <valerio.setti@nordicsemi.no>
diff --git a/include/mbedtls/config_psa.h b/include/mbedtls/config_psa.h
index de961ec..5f3d0f3 100644
--- a/include/mbedtls/config_psa.h
+++ b/include/mbedtls/config_psa.h
@@ -34,7 +34,11 @@
  * before we deduce what built-ins are required. */
 #include "psa/crypto_adjust_config_key_pair_types.h"
 
+#if defined(MBEDTLS_PSA_CRYPTO_C)
+/* If we are implementing PSA crypto ourselves, then we want to enable the
+ * required built-ins. Otherwise, PSA features will be provided by the server. */
 #include "mbedtls/config_adjust_legacy_from_psa.h"
+#endif
 
 #else /* MBEDTLS_PSA_CRYPTO_CONFIG */