scsi: core: Use rq_dma_dir in scsi_setup_cmnd()

Link: https://lore.kernel.org/r/20201005084130.143273-6-hch@lst.de


Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>