gpio: Add Cadence GPIO driver

This patch adds a driver for Cadence GPIO controller.

It can be enabled with GPIO_CADENCE Kconfig option.
It uses generic GPIO infrastructure and works
as an interrupt controller.
At the moment it only supports level sensitive irqs.

Signed-off-by: Jan Kotas <jank@cadence.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/gpio/Makefile

@@ -37,6 +37,7 @@ obj-$(CONFIG_GPIO_BCM_KONA)	+= gpio-bcm-kona.o
 obj-$(CONFIG_GPIO_BD9571MWV)	+= gpio-bd9571mwv.o
 obj-$(CONFIG_GPIO_BRCMSTB)	+= gpio-brcmstb.o
 obj-$(CONFIG_GPIO_BT8XX)	+= gpio-bt8xx.o
+obj-$(CONFIG_GPIO_CADENCE)	+= gpio-cadence.o
 obj-$(CONFIG_GPIO_CLPS711X)	+= gpio-clps711x.o
 obj-$(CONFIG_GPIO_CS5535)	+= gpio-cs5535.o
 obj-$(CONFIG_GPIO_CRYSTAL_COVE)	+= gpio-crystalcove.o