gpio/mxc: add chained_irq_enter/exit() to mx3_gpio_irq_handler()

The mx3_gpio_irq_handler() is also called on imx6q which has GIC as
the primary interrupt controller.  As GIC implements the fasteoi flow
control, we need to add chained_irq_enter/exit() to
mx3_gpio_irq_handler() for signaling EOI, otherwise system will hang
whenever there is a gpio irq triggered.

v2: use chained_irq_{enter,exit}()
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>

drivers/gpio/gpio-mxc.c

@@ -30,6 +30,7 @@
 #include <linux/of.h>
 #include <linux/of_device.h>
 #include <asm-generic/bug.h>
+#include <asm/mach/irq.h>
 
 enum mxc_gpio_hwtype {
 	IMX1_GPIO,	/* runs on i.mx1 */
@@ -232,10 +233,15 @@ static void mx3_gpio_irq_handler(u32 irq, struct irq_desc *desc)
 {
 	u32 irq_stat;
 	struct mxc_gpio_port *port = irq_get_handler_data(irq);
+	struct irq_chip *chip = irq_get_chip(irq);
+
+	chained_irq_enter(chip, desc);
 
 	irq_stat = readl(port->base + GPIO_ISR) & readl(port->base + GPIO_IMR);
 
 	mxc_gpio_irq_handler(port, irq_stat);
+
+	chained_irq_exit(chip, desc);
 }
 
 /* MX2 has one interrupt *for all* gpio ports */