[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-tb0287.c b/arch/mips/pci/fixup-tb0287.c
index fbe6bcb..267ab3d 100644
--- a/arch/mips/pci/fixup-tb0287.c
+++ b/arch/mips/pci/fixup-tb0287.c
@@ -22,7 +22,7 @@
 
 #include <asm/vr41xx/tb0287.h>
 
-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)
 {
 	unsigned char bus;
 	int irq = -1;