nvme: Use blk_rq_map_user_io helper

User blk_rq_map_user_io instead of duplicating the same code at
different places

Signed-off-by: Anuj Gupta <anuj20.g@samsung.com>
Link: https://lore.kernel.org/r/20220930062749.152261-6-anuj20.g@samsung.com


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