sunxi: add gpio driver

This patch enables CONFIG_CMD_GPIO for the Allwinner (sunxi) platform as well
as providing the common gpio API (gpio_request/free, direction in/out, get/set
etc).

Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Ma Haijun <mahaijuns@gmail.com>
Signed-off-by: Oliver Schinagl <oliver@schinagl.nl>
Signed-off-by: Ian Campbell <ijc@hellion.org.uk>
Cc: Henrik Nordström <henrik@henriknordstrom.net>
Cc: Tom Cubie <Mr.hipboi@gmail.com>
Acked-by: Hans de Goede <hdegoede@redhat.com>
diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile
index 4e001e1..86813b9 100644
--- a/drivers/gpio/Makefile
+++ b/drivers/gpio/Makefile
@@ -34,3 +34,4 @@
 obj-$(CONFIG_ADI_GPIO2)	+= adi_gpio2.o
 obj-$(CONFIG_TCA642X)		+= tca642x.o
 oby-$(CONFIG_SX151X)		+= sx151x.o
+obj-$(CONFIG_SUNXI_GPIO)	+= sunxi_gpio.o