pata_optidma: 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: Reimar Döffinger <[e-mail]>
Signed-off-by: Damien Le Moal <[e-mail]>

drivers/ata/pata_optidma.c

···
 	if (pair) {
 		u8 pair_addr;
 		/* Hardware constraint */
-		if (pair->dma_mode)
+		if (ata_dma_enabled(pair))
 			pair_addr = 0;
 		else
 			pair_addr = addr_timing[pci_clock][pair->pio_mode - XFER_PIO_0];
···
 	};
 	if (!ata_dev_enabled(adev))
 		return 0;
-	if (adev->dma_mode)
+	if (ata_dma_enabled(adev))
 		return adev->dma_mode - XFER_MW_DMA_0;
 	return bits43[adev->pio_mode - XFER_PIO_0];
 }