gpio/mxc: convert gpio-mxc to use generic irq chip

The patch converts gpio-mxc driver to use generic irq chip.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Acked-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index 89a6a34..4e2d612 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -96,6 +96,7 @@
 	def_bool y
 	depends on ARCH_MXC
 	select GPIO_GENERIC
+	select GENERIC_IRQ_CHIP
 
 config GPIO_MXS
 	def_bool y