ns9xxx: fix sparse warning

The actual warning is
	arch/arm/mach-ns9xxx/irq.c:65:6: warning: symbol 'handle_prio_irq' was not declared. Should it be static?

Signed-off-by: Uwe Kleine-König <Uwe.Kleine-Koenig@digi.com>
diff --git a/arch/arm/mach-ns9xxx/irq.c b/arch/arm/mach-ns9xxx/irq.c
index 75f2070..bfd906b 100644
--- a/arch/arm/mach-ns9xxx/irq.c
+++ b/arch/arm/mach-ns9xxx/irq.c
@@ -56,7 +56,7 @@
 #if 0
 #define handle_irq handle_level_irq
 #else
-void handle_prio_irq(unsigned int irq, struct irq_desc *desc)
+static void handle_prio_irq(unsigned int irq, struct irq_desc *desc)
 {
 	unsigned int cpu = smp_processor_id();
 	struct irqaction *action;