scsi: sun3_scsi: Use scsi_cmd_to_rq() instead of scsi_cmnd.request

Prepare for removal of the request pointer by using scsi_cmd_to_rq()
instead. This patch does not change any functionality.

Link: https://lore.kernel.org/r/20210809230355.8186-46-bvanassche@acm.org
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/sun3_scsi.c

@@ -336,7 +336,7 @@ static int sun3scsi_dma_xfer_len(struct NCR5380_hostdata *hostdata,
 {
 	int wanted_len = cmd->SCp.this_residual;
 
-	if (wanted_len < DMA_MIN_SIZE || blk_rq_is_passthrough(cmd->request))
+	if (wanted_len < DMA_MIN_SIZE || blk_rq_is_passthrough(scsi_cmd_to_rq(cmd)))
 		return 0;
 
 	return wanted_len;