Fix guard for PSA->MD error conversion

Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>
diff --git a/include/mbedtls/psa_util.h b/include/mbedtls/psa_util.h
index f1a49ec..1971646 100644
--- a/include/mbedtls/psa_util.h
+++ b/include/mbedtls/psa_util.h
@@ -373,7 +373,7 @@
     int16_t mbedtls_error;
 } mbedtls_error_pair_t;
 
-#if !defined(MBEDTLS_MD_C) || !defined(MBEDTLS_MD5_C) || defined(MBEDTLS_USE_PSA_CRYPTO)
+#if defined(MBEDTLS_MD_LIGHT)
 extern const mbedtls_error_pair_t psa_to_md_errors[4];
 #endif