[MIPS] rbtx4938: Fix warnings

linux/arch/mips/pci/fixup-tx4938.c:21:5: warning: symbol 'pci_get_irq' was not declared. Should it be static?
linux/arch/mips/pci/fixup-tx4938.c:76: warning: passing argument 1 of 'pci_get_irq' discards qualifiers from pointer target type
Signed-off-by: NAtsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: NRalf Baechle <ralf@linux-mips.org>

arch/mips/pci/fixup-tx4938.c

@@ -18,7 +18,7 @@
 
 extern struct pci_controller tx4938_pci_controller[];
 
-int pci_get_irq(struct pci_dev *dev, int pin)
+static int pci_get_irq(const struct pci_dev *dev, int pin)
 {
 	int irq = pin;
 	u8 slot = PCI_SLOT(dev->devfn);