nvme: move nvme_setup_flush and nvme_setup_rw to common code

nvme: move nvme_setup_flush and nvme_setup_rw to common code

And mark them inline so that we don't slow down the I/O submission path by
having to turn it into a forced out of line call.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
(cherry picked from commit 22944e9981db1e496d983298fd420a8c6b758c80)

Orabug: 25130845
Signed-off-by: Ashok Vairavan <ashok.vairavan@oracle.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>