gpio: pl061: convert driver to use gpiolib irqchip

This converts the PL061 driver to register its chained irq
handler and irqchip using the helpers in the gpiolib core.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index 51c7825..92d8e9a 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -247,6 +247,7 @@
 	bool "PrimeCell PL061 GPIO support"
 	depends on ARM_AMBA
 	select IRQ_DOMAIN
+	select GPIOLIB_IRQCHIP
 	help
 	  Say yes here to support the PrimeCell PL061 GPIO device