PCI: use config space encoding in pci_get_interrupt_pin()

This patch makes pci_get_interrupt_pin() return values encoded
the same way as the "Interrupt Pin" value in PCI config space,
i.e., 1=INTA, ..., 4=INTD.

pirq_bios_set() is the only in-tree caller of pci_get_interrupt_pin()
and pci_get_interrupt_pin() is not exported.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: hpa@zytor.com
Signed-off-by: Bjorn Helgaas <bjorn.helgaas@hp.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>

arch/x86/pci/irq.c

@@ -533,7 +533,7 @@ static int pirq_bios_set(struct pci_dev *router, struct pci_dev *dev, int pirq,
 {
 	struct pci_dev *bridge;
 	int pin = pci_get_interrupt_pin(dev, &bridge);
-	return pcibios_set_irq_routing(bridge, pin, irq);
+	return pcibios_set_irq_routing(bridge, pin - 1, irq);
 }
 
 #endif

drivers/pci/pci.c

@@ -1374,9 +1374,9 @@ pci_get_interrupt_pin(struct pci_dev *dev, struct pci_dev **bridge)
 	pin = dev->pin;
 	if (!pin)
 		return -1;
-	pin--;
+
 	while (dev->bus->self) {
-		pin = (pin + PCI_SLOT(dev->devfn)) % 4;
+		pin = (((pin - 1) + PCI_SLOT(dev->devfn)) % 4) + 1;
 		dev = dev->bus->self;
 	}
 	*bridge = dev;