PCI: Provide a default pcibios_update_irq()

Most architectures implement this in exactly the same way. Instead of
having each architecture duplicate this function, provide a single
implementation in the core and make it a weak symbol so that it can be
overridden on architectures where it is required.

Signed-off-by: Thierry Reding <thierry.reding@avionic-design.de>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
diff --git a/drivers/pci/setup-irq.c b/drivers/pci/setup-irq.c
index 270ae7b..9bd6864 100644
--- a/drivers/pci/setup-irq.c
+++ b/drivers/pci/setup-irq.c
@@ -17,6 +17,11 @@
 #include <linux/ioport.h>
 #include <linux/cache.h>
 
+void __weak pcibios_update_irq(struct pci_dev *dev, int irq)
+{
+	dev_dbg(&dev->dev, "assigning IRQ %02d\n", irq);
+	pci_write_config_byte(dev, PCI_INTERRUPT_LINE, irq);
+}
 
 static void
 pdev_fixup_irq(struct pci_dev *dev,