PCI: Add pci_add_dma_alias() to abstract implementation

Add a pci_add_dma_alias() interface to encapsulate the details of adding an
alias.  No functional change intended.

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Alex Williamson <alex.williamson@redhat.com>
diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
index 8e67802..e45a7a8 100644
--- a/drivers/pci/quirks.c
+++ b/drivers/pci/quirks.c
@@ -3610,10 +3610,8 @@
 
 static void quirk_dma_func0_alias(struct pci_dev *dev)
 {
-	if (PCI_FUNC(dev->devfn) != 0) {
-		dev->dma_alias_devfn = PCI_DEVFN(PCI_SLOT(dev->devfn), 0);
-		dev->dev_flags |= PCI_DEV_FLAGS_DMA_ALIAS_DEVFN;
-	}
+	if (PCI_FUNC(dev->devfn) != 0)
+		pci_add_dma_alias(dev, PCI_DEVFN(PCI_SLOT(dev->devfn), 0));
 }
 
 /*
@@ -3626,10 +3624,8 @@
 
 static void quirk_dma_func1_alias(struct pci_dev *dev)
 {
-	if (PCI_FUNC(dev->devfn) != 1) {
-		dev->dma_alias_devfn = PCI_DEVFN(PCI_SLOT(dev->devfn), 1);
-		dev->dev_flags |= PCI_DEV_FLAGS_DMA_ALIAS_DEVFN;
-	}
+	if (PCI_FUNC(dev->devfn) != 1)
+		pci_add_dma_alias(dev, PCI_DEVFN(PCI_SLOT(dev->devfn), 1));
 }
 
 /*
@@ -3696,11 +3692,10 @@
 
 	id = pci_match_id(fixed_dma_alias_tbl, dev);
 	if (id) {
-		dev->dma_alias_devfn = id->driver_data;
-		dev->dev_flags |= PCI_DEV_FLAGS_DMA_ALIAS_DEVFN;
+		pci_add_dma_alias(dev, id->driver_data);
 		dev_info(&dev->dev, "Enabling fixed DMA alias to %02x.%d\n",
-			 PCI_SLOT(dev->dma_alias_devfn),
-			 PCI_FUNC(dev->dma_alias_devfn));
+			 PCI_SLOT(id->driver_data),
+			 PCI_FUNC(id->driver_data));
 	}
 }