nvme: set REQ_ALLOC_CACHE for uring-passthru request

This patch sets REQ_ALLOC_CACHE flag for uring-passthru requests.
This is a prep-patch so that normal / IRQ-driven uring-passthru
I/Os can also leverage bio-cache.

Signed-off-by: Anuj Gupta <anuj20.g@samsung.com>
Signed-off-by: Kanchan Joshi <joshi.k@samsung.com>
Link: https://lore.kernel.org/r/20230117120638.72254-2-anuj20.g@samsung.com


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