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/pci/sl82c105.c b/drivers/ide/pci/sl82c105.c
index 2c2fe59..c2127cb 100644
--- a/drivers/ide/pci/sl82c105.c
+++ b/drivers/ide/pci/sl82c105.c
@@ -296,9 +296,6 @@
 	hwif->dma_start			= &sl82c105_dma_start;
 	hwif->ide_dma_end		= &sl82c105_dma_end;
 	hwif->dma_timeout		= &sl82c105_dma_timeout;
-
-	if (hwif->mate)
-		hwif->serialized = hwif->mate->serialized = 1;
 }
 
 static const struct ide_port_ops sl82c105_port_ops = {
@@ -319,6 +316,7 @@
 #if defined(CONFIG_LOPEC) || defined(CONFIG_SANDPOINT)
 			  IDE_HFLAG_FORCE_LEGACY_IRQS |
 #endif
+			  IDE_HFLAG_SERIALIZE_DMA |
 			  IDE_HFLAG_NO_AUTODMA,
 	.pio_mask	= ATA_PIO5,
 	.mwdma_mask	= ATA_MWDMA2,
@@ -338,6 +336,7 @@
 				 "revision %d, BM-DMA disabled\n", rev);
 		d.init_hwif = NULL;
 		d.mwdma_mask = 0;
+		d.host_flags &= ~IDE_HFLAG_SERIALIZE_DMA;
 	}
 
 	return ide_setup_pci_device(dev, &d);