engines/nvme: pass offset and len instead of io_u

engines/nvme: pass offset and len instead of io_u

Remove io_u dependency while calculating start and number of lba.
This is a prep patch for multi-range trim support where an io_u entry
will contain multiple start offset and buffer len.

Signed-off-by: Ankit Kumar <ankit.kumar@samsung.com>
Link: https://lore.kernel.org/r/20240215151812.138370-3-ankit.kumar@samsung.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>