[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/pci-bcm1480.c b/arch/mips/pci/pci-bcm1480.c
index d7b9e13..2b4e30c 100644
--- a/arch/mips/pci/pci-bcm1480.c
+++ b/arch/mips/pci/pci-bcm1480.c
@@ -74,8 +74,9 @@
 	*(u32 *)(cfg_space + (addr & ~3)) = data;
 }
 
-int pcibios_map_irq(struct pci_dev *dev, u8 slot, u8 pin)
+int pcibios_map_irq(const struct pci_dev *dev, u8 slot, u8 pin)
 {
+	This is b0rked.
 	return dev->irq;
 }