ide: remove ->dma_{status,command} fields from ide_hwif_t

* Use ->dma_base + offset instead of ->dma_{status,command}
  and remove no longer needed ->dma_{status,command}.

While at it:

* Use ATA_DMA_* defines.

There should be no functional changes caused by this patch.

Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
diff --git a/drivers/ide/pci/sl82c105.c b/drivers/ide/pci/sl82c105.c
index 6efbde2..f82a650 100644
--- a/drivers/ide/pci/sl82c105.c
+++ b/drivers/ide/pci/sl82c105.c
@@ -157,9 +157,9 @@
 	 * Was DMA enabled?  If so, disable it - we're resetting the
 	 * host.  The IDE layer will be handling the drive for us.
 	 */
-	dma_cmd = inb(hwif->dma_command);
+	dma_cmd = inb(hwif->dma_base + ATA_DMA_CMD);
 	if (dma_cmd & 1) {
-		outb(dma_cmd & ~1, hwif->dma_command);
+		outb(dma_cmd & ~1, hwif->dma_base + ATA_DMA_CMD);
 		printk("sl82c105: DMA was enabled\n");
 	}