rockchip: gpio: Add rockchip GPIO driver

This supports RK3288 at present. It does not implement functions or support
for pull up/down.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile
index ba18594..c58aa4d 100644
--- a/drivers/gpio/Makefile
+++ b/drivers/gpio/Makefile
@@ -21,6 +21,7 @@
 obj-$(CONFIG_MXS_GPIO)	+= mxs_gpio.o
 obj-$(CONFIG_PCA953X)		+= pca953x.o
 obj-$(CONFIG_PCA9698)		+= pca9698.o
+obj-$(CONFIG_ROCKCHIP_GPIO)	+= rk_gpio.o
 obj-$(CONFIG_S5P)		+= s5p_gpio.o
 obj-$(CONFIG_SANDBOX_GPIO)	+= sandbox.o
 obj-$(CONFIG_SPEAR_GPIO)	+= spear_gpio.o