[PATCH] bug in V-link handling (arch/i386/pci/irq.c)

	Via southbridges use register 0x3c of the on-board devices (USB and
AC97) to control interrupt routing for those.  In drivers/pci/quirks.c we
set it correctly (dev->irq & 15).  However, in pirq_enable_irq() where the
second half of that stuff lives, we forget to apply the mask.

	That's what causes problems with ioapic on via motherboards in 2.6.
One-liner below ACKed by Alan, verified on via-based boxen here, obviously
doesn't affect non-via ones (we only set interrupt_line_quirk for via
chipsets). 

arch/i386/pci/irq.c

@@ -1030,7 +1030,7 @@ int pirq_enable_irq(struct pci_dev *dev)
 	/* VIA bridges use interrupt line for apic/pci steering across
 	   the V-Link */
 	else if (interrupt_line_quirk)
-		pci_write_config_byte(dev, PCI_INTERRUPT_LINE, dev->irq);
+		pci_write_config_byte(dev, PCI_INTERRUPT_LINE, dev->irq & 15);
 	return 0;
 }