Add missing ifdefs

Make sure that the error translating functions
are only defined when they're used.
Signed-off-by: Andrzej Kurek <andrzej.kurek@arm.com>
diff --git a/library/ssl_tls12_client.c b/library/ssl_tls12_client.c
index 75b79bf..ade68a9 100644
--- a/library/ssl_tls12_client.c
+++ b/library/ssl_tls12_client.c
@@ -33,6 +33,7 @@
 #if defined(MBEDTLS_USE_PSA_CRYPTO)
 #include "mbedtls/psa_util.h"
 #include "psa/crypto.h"
+#if defined(MBEDTLS_KEY_EXCHANGE_ECDHE_PSK_ENABLED)
 /* Define a local translating function to save code size by not using too many
  * arguments in each translating place. */
 static int local_err_translation(psa_status_t status)
@@ -42,6 +43,7 @@
                                  psa_generic_status_to_mbedtls);
 }
 #define PSA_TO_MBEDTLS_ERR(status) local_err_translation(status)
+#endif /* MBEDTLS_KEY_EXCHANGE_ECDHE_PSK_ENABLED */
 #endif /* MBEDTLS_USE_PSA_CRYPTO */
 
 #include <string.h>