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>

arch/ia64/pci/pci.c

@@ -461,14 +461,6 @@ void pcibios_set_master (struct pci_dev *dev)
 	/* No special bus mastering setup handling */
 }
 
-void
-pcibios_update_irq (struct pci_dev *dev, int irq)
-{
-	pci_write_config_byte(dev, PCI_INTERRUPT_LINE, irq);
-
-	/* ??? FIXME -- record old value for shutdown.  */
-}
-
 int
 pcibios_enable_device (struct pci_dev *dev, int mask)
 {