ubifs: ensure zero err is returned on successful return

err is no longer being set on a successful return path, causing
a garbage value being returned. Fix this by setting err to zero
for the successful return path.

Found with static analysis by CoverityScan, CID 1389473

Fixes: 7799953b ("ubifs: Implement encrypt/decrypt for all IO")
Signed-off-by: NColin Ian King <colin.king@canonical.com>
Signed-off-by: NRichard Weinberger <richard@nod.at>

fs/ubifs/journal.c

@@ -1319,6 +1319,7 @@ static int truncate_data_node(const struct ubifs_info *c, const struct inode *in
 	dn->compr_type = cpu_to_le16(compr_type);
 	dn->size = cpu_to_le32(*new_len);
 	*new_len = UBIFS_DATA_NODE_SZ + out_len;
+	err = 0;
 out:
 	kfree(buf);
 	return err;