fs/buffer: Fix the ll_rw_block() kernel-doc header

fs/buffer: Fix the ll_rw_block() kernel-doc header

Bring the ll_rw_block() kernel-doc header again in sync with the
function prototype.

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Jan Kara <jack@suse.cz>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Fixes: bb89288ab706 ("fs/buffer: Combine two submit_bh() and ll_rw_block() arguments")
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20220715184735.2326034-2-bvanassche@acm.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>