sunxi: add sun7i pinmux and gpio support

sunxi: add sun7i pinmux and gpio support

This patch adds the basic pinmux and gpio support for the Allwinner A20 (sun7i)
processor. This code will not been compiled until the build is hooked up in a
later patch. It has been split out to keep the patches manageable.

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: Henrik Nordström <henrik@henriknordstrom.net>
Signed-off-by: Ian Campbell <ijc@hellion.org.uk>
Reviewed-by: Tom Rini <trini@ti.com>
Acked-by: Marek Vasut <marex@denx.de>
Cc: Stefan Roese <sr@denx.de>
Cc: Tom Cubie <Mr.hipboi@gmail.com>
Reviewed-by: Tom Rini <trini@ti.com>