Btrfs: move over to use ->update_time

Btrfs had been doing it's own file_update_time so we could catch ENOSPC
properly, so just update our btrfs_update_time to work with the new stuff and
then we'll be fancy later.  Thanks,

Signed-off-by: Josef Bacik <josef@redhat.com>

fs/btrfs/file.c

@@ -1404,7 +1404,7 @@ static ssize_t btrfs_file_aio_write(struct kiocb *iocb,
 		goto out;
 	}
 
-	err = btrfs_update_time(file);
+	err = file_update_time(file);
 	if (err) {
 		mutex_unlock(&inode->i_mutex);
 		goto out;