nvme: helper for uring-passthrough checks

Factor out a helper consolidating the error checks, and fix typo in a
comment too. This is in preparation to support admin commands on this
path.

Signed-off-by: Kanchan Joshi <joshi.k@samsung.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20220520090630.70394-2-joshi.k@samsung.com


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