ARM: iop: make iop_handle_irq() static

The build bots complain about iop_handle_irq() not being declared so
let's make it static instead.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

arch/arm/mach-iop32x/irq.c

@@ -59,7 +59,7 @@ struct irq_chip ext_chip = {
 	.irq_unmask	= iop32x_irq_unmask,
 };
 
-void iop_handle_irq(struct pt_regs *regs)
+static void iop_handle_irq(struct pt_regs *regs)
 {
 	u32 mask;