ARM: mxs: icoll: Fix sparse warning

Fix the following sparse warning:

arch/arm/mach-mxs/icoll.c:103:13: warning: symbol 'icoll_of_init' was not declared. Should it be static?
Signed-off-by: NFabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: NShawn Guo <shawn.guo@linaro.org>

arch/arm/mach-mxs/icoll.c

@@ -100,7 +100,7 @@ static struct irq_domain_ops icoll_irq_domain_ops = {
 	.xlate = irq_domain_xlate_onecell,
 };
 
-void __init icoll_of_init(struct device_node *np,
+static void __init icoll_of_init(struct device_node *np,
 			  struct device_node *interrupt_parent)
 {
 	/*