Add devicetree bindings for MediaTek MT6779 pinctrl driver.

Signed-off-by: Andy Teng <andy.teng@mediatek.com>
Signed-off-by: Hanks Chen <hanks.chen@mediatek.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/1596115816-11758-2-git-send-email-hanks.chen@mediatek.com


Signed-off-by: Linus Walleij <linus.walleij@linaro.org>