nvme: mark nvme_setup_passsthru() inline

[ Upstream commit 7a366046 ]

Since nvmet_setup_passthru() function falls in fast path when called
from the NVMeOF passthru backend, make it inline.

Signed-off-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>