block: remove unused nseg parameter

We are no longer using nr_segs, after blk_mq_attempt_bio_merge was moved
out of blk_mq_get_new_request.

Signed-off-by: Nitesh Shetty <nj.shetty@samsung.com>
Link: https://lore.kernel.org/r/20250401044348.15588-1-nj.shetty@samsung.com


Signed-off-by: Jens Axboe <axboe@kernel.dk>