Add Intel ICH6 irq router.

arch/i386/pci/irq.c

@@ -479,6 +479,7 @@ static __init int intel_router_probe(struct irq_router *r, struct pci_dev *route
 		case PCI_DEVICE_ID_INTEL_82801E_0:
 		case PCI_DEVICE_ID_INTEL_82801EB_0:
 		case PCI_DEVICE_ID_INTEL_ESB_0:
+		case PCI_DEVICE_ID_INTEL_ICH6_0:
 			r->name = "PIIX/ICH";
 			r->get = pirq_piix_get;
 			r->set = pirq_piix_set;