scsi: libsas: Set data_dir as DMA_NONE if libata marks qc as NODATA

It was discovered that sdparm will fail when attempting to disable write
cache on a SATA disk connected via libsas.

In the ATA command set the write cache state is controlled through the SET
FEATURES operation. This is roughly corresponds to MODE SELECT in SCSI and
the latter command is what is used in the SCSI-ATA translation layer. A
subtle difference is that a MODE SELECT carries data whereas SET FEATURES
is defined as a non-data command in ATA.

Set the DMA data direction to DMA_NONE if the requested ATA command is
identified as non-data.

[mkp: commit desc]

Fixes: fa1c1e8f ("[SCSI] Add SATA support to libsas")
Link: https://lore.kernel.org/r/1598426666-54544-1-git-send-email-luojiaxing@huawei.comReviewed-by: John Garry <john.garry@huawei.com>
Reviewed-by: Jason Yan <yanaijie@huawei.com>
Signed-off-by: Luo Jiaxing <luojiaxing@huawei.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/libsas/sas_ata.c

@@ -209,6 +209,9 @@ static unsigned int sas_ata_qc_issue(struct ata_queued_cmd *qc)
 		task->num_scatter = si;
 	}
 
+	if (qc->tf.protocol == ATA_PROT_NODATA)
+		task->data_dir = DMA_NONE;
+	else
 		task->data_dir = qc->dma_dir;
 	task->scatter = qc->sg;
 	task->ata_task.retry_count = 1;