dm: gpio: hi6220: Add a hi6220 GPIO driver model driver.

This patch adds support for the GPIO perif found on hi6220
SoC.

Signed-off-by: Peter Griffin <peter.griffin@linaro.org>
diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile
index 67c6374..26f2574 100644
--- a/drivers/gpio/Makefile
+++ b/drivers/gpio/Makefile
@@ -42,3 +42,5 @@
 obj-$(CONFIG_STM32_GPIO)	+= stm32_gpio.o
 obj-$(CONFIG_ZYNQ_GPIO)		+= zynq_gpio.o
 obj-$(CONFIG_VYBRID_GPIO)	+= vybrid_gpio.o
+obj-$(CONFIG_HIKEY_GPIO)	+= hi6220_gpio.o
+