ide: add IDE_HFLAG_SERIALIZE_DMA host flag

* Add IDE_HFLAG_SERIALIZE_DMA host flag to serialize ports
  if DMA is available and handle it in ide_init_port().

* Convert sl82c105 host driver to use this new flag.

Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
diff --git a/drivers/ide/ide-probe.c b/drivers/ide/ide-probe.c
index e031686..b58eb79 100644
--- a/drivers/ide/ide-probe.c
+++ b/drivers/ide/ide-probe.c
@@ -1367,8 +1367,11 @@
 	if (hwif->chipset != ide_dtc2278 || hwif->channel == 0)
 		hwif->port_ops = d->port_ops;
 
-	if ((d->host_flags & IDE_HFLAG_SERIALIZE) && hwif->mate)
-		hwif->mate->serialized = hwif->serialized = 1;
+	if ((d->host_flags & IDE_HFLAG_SERIALIZE) ||
+	    ((d->host_flags & IDE_HFLAG_SERIALIZE_DMA) && hwif->dma_base)) {
+		if (hwif->mate)
+			hwif->mate->serialized = hwif->serialized = 1;
+	}
 
 	hwif->swdma_mask = d->swdma_mask;
 	hwif->mwdma_mask = d->mwdma_mask;