libata-scsi: fix checking of DMA state

Checking if DMA is enabled should be done via the
ata_dma_enabled helper function, since the init state
0xff indicates disabled.
Change based on code review, not tested due to lack of hardware.
Signed-off-by: NReimar Döffinger <Reimar.Doeffinger@gmx.de>
Signed-off-by: NDamien Le Moal <damien.lemoal@wdc.com>

drivers/ata/libata-scsi.c

@@ -2981,7 +2981,7 @@ static unsigned int ata_scsi_pass_thru(struct ata_queued_cmd *qc)
 	ata_qc_set_pc_nbytes(qc);
 
 	/* We may not issue DMA commands if no DMA mode is set */
-	if (tf->protocol == ATA_PROT_DMA && dev->dma_mode == 0) {
+	if (tf->protocol == ATA_PROT_DMA && !ata_dma_enabled(dev)) {
 		fp = 1;
 		goto invalid_fld;
 	}
@@ -3131,7 +3131,7 @@ static unsigned int ata_scsi_write_same_xlat(struct ata_queued_cmd *qc)
 	u8 unmap = cdb[1] & 0x8;
 
 	/* we may not issue DMA commands if no DMA mode is set */
-	if (unlikely(!dev->dma_mode))
+	if (unlikely(!ata_dma_enabled(dev)))
 		goto invalid_opcode;
 
 	/*