[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>
diff --git a/arch/mips/pci/fixup-wrppmc.c b/arch/mips/pci/fixup-wrppmc.c
index 3357c13..3d27754 100644
--- a/arch/mips/pci/fixup-wrppmc.c
+++ b/arch/mips/pci/fixup-wrppmc.c
@@ -25,7 +25,7 @@
 	[6] = {0, WRPPMC_PCI_INTA_IRQ, 0, 0, 0},
 };
 
-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 pci_irq_tab[slot][pin];
 }