sunxi: gpio: Add .xlate function for gpio phandle resolution

sunxi uses a 2 cell phandle for gpio bindings. Also there are no
seperate nodes for each pin bank.

Add a custom .xlate function to map gpio phandles to the correct
pin bank device. This fixes gpio_request_by_name usage.

Fixes: 7aa97485 ("dm: sunxi: Modify the GPIO driver to support driver
		      model")
Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>