gpio: stmpe: switch to use gpiolib irqchip helpers

This switches the STMPE driver to use the gpiolib irqchip
helpers.

Tested-by: Silvio Fricke <silvio.fricke@gmail.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index 4a1b511..690904a 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -573,6 +573,7 @@
 config GPIO_STMPE
 	bool "STMPE GPIOs"
 	depends on MFD_STMPE
+	select GPIOLIB_IRQCHIP
 	help
 	  This enables support for the GPIOs found on the STMPE I/O
 	  Expanders.