[MIPS] EV64120: Include <asm/irq.h> to fix warning.

arch/mips/pci/pci-ev64120.c:10: warning: implicit declaration of function 'allocate_irqno'
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/pci/pci-ev64120.c

 #include <linux/pci.h>
+#include <asm/irq.h>
 
 int __init pcibios_map_irq(struct pci_dev *dev, u8 slot, u8 pin)
 {