X.509: Fix error code in x509_cert_parse()

We forgot to set the error code on this path so it could result in
returning NULL which leads to a NULL dereference.

Fixes: db6c43bd21 ("crypto: KEYS: convert public key and digsig asym to the akcipher api")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

crypto/asymmetric_keys/x509_cert_parser.c

@@ -102,6 +102,7 @@ struct x509_certificate *x509_cert_parse(const void *data, size_t datalen)
 		}
 	}
 
+	ret = -ENOMEM;
 	cert->pub->key = kmemdup(ctx->key, ctx->key_size, GFP_KERNEL);
 	if (!cert->pub->key)
 		goto error_decode;