MIPS: BCM47XX: add asmlinkage to plat_irq_dispatch()

plat_irq_dispatch() is called from asm code, add asmlinkage.
Signed-off-by: NHauke Mehrtens <hauke@hauke-m.de>
Signed-off-by: NJohn Crispin <blogic@openwrt.org>
Patchwork: http://patchwork.linux-mips.org/patch/6043/

arch/mips/bcm47xx/irq.c

@@ -28,7 +28,7 @@
 #include <asm/irq_cpu.h>
 #include <bcm47xx.h>
 
-void plat_irq_dispatch(void)
+asmlinkage void plat_irq_dispatch(void)
 {
 	u32 cause;