gpio/mxc: add chained_irq_enter/exit() to mx2_gpio_irq_handler

Similar to commit

	0e44b6ec (gpio/mxc: add chained_irq_enter/exit() to mx3_gpio_irq_handler())

. It doesn't seem to be critical to make the irqs work, but still it is
more correct.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Acked-by: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/gpio/gpio-mxc.c

@@ -292,6 +292,9 @@ static void mx2_gpio_irq_handler(u32 irq, struct irq_desc *desc)
 {
 	u32 irq_msk, irq_stat;
 	struct mxc_gpio_port *port;
+	struct irq_chip *chip = irq_get_chip(irq);
+
+	chained_irq_enter(chip, desc);
 
 	/* walk through all interrupt status registers */
 	list_for_each_entry(port, &mxc_gpio_ports, node) {
@@ -303,6 +306,7 @@ static void mx2_gpio_irq_handler(u32 irq, struct irq_desc *desc)
 		if (irq_stat)
 			mxc_gpio_irq_handler(port, irq_stat);
 	}
+	chained_irq_exit(chip, desc);
 }
 
 /*