jbd: Fix comment to match the code in journal_start()

journal_start returns an ERR_PTR() value rather than NULL on failure.

Cc: Jan Kara <jack@suse.cz>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
1 file changed