arm/imx: fix return type of callback passed to of_irq_init()

The of_irq_init() expects the callback passed by .data of of_device_id
return 'int' instead of 'void'.  This patch fixes it to have
irq_init_cb() return the correct value, and in turn have the secondary
interrupt controller (gpio in this case) initialized properly and also
eliminate the error message 'of_irq_init: children remain, but no
parents' which was overlooked before.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
diff --git a/arch/arm/mach-mx5/imx51-dt.c b/arch/arm/mach-mx5/imx51-dt.c
index ccc6158..3451a46 100644
--- a/arch/arm/mach-mx5/imx51-dt.c
+++ b/arch/arm/mach-mx5/imx51-dt.c
@@ -44,13 +44,14 @@
 	{ /* sentinel */ }
 };
 
-static void __init imx51_tzic_add_irq_domain(struct device_node *np,
+static int __init imx51_tzic_add_irq_domain(struct device_node *np,
 				struct device_node *interrupt_parent)
 {
 	irq_domain_add_simple(np, 0);
+	return 0;
 }
 
-static void __init imx51_gpio_add_irq_domain(struct device_node *np,
+static int __init imx51_gpio_add_irq_domain(struct device_node *np,
 				struct device_node *interrupt_parent)
 {
 	static int gpio_irq_base = MXC_GPIO_IRQ_START + ARCH_NR_GPIOS -
@@ -58,6 +59,8 @@
 
 	irq_domain_add_simple(np, gpio_irq_base);
 	gpio_irq_base += 32;
+
+	return 0;
 }
 
 static const struct of_device_id imx51_irq_match[] __initconst = {