target/pscsi: remove pscsi_get_bio

Remove pscsi_get_bio and simplify the code flow in the only caller.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Link: https://lore.kernel.org/r/20220406061228.410163-4-hch@lst.de


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