[MIPS] PCI: Make dev pointer argument of pcibios_map_irq const.

This is to break the code of people who think they are supposed to scribble
into the pci device structure - it's off limits.

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/pci/fixup-capcella.c

@@ -38,7 +38,7 @@ static char irq_tab_capcella[][5] __initdata = {
  [14] = { -1, INTA, INTB, INTC, INTD }
 };
 
-int __init pcibios_map_irq(struct pci_dev *dev, u8 slot, u8 pin)
+int __init pcibios_map_irq(const struct pci_dev *dev, u8 slot, u8 pin)
 {
 	return irq_tab_capcella[slot][pin];
 }