pinctrl: mediatek: add pinctrl support for MT7629 SoC

This adds MT7629 pinctrl driver based on MediaTek pinctrl-moore core.

Signed-off-by: Ryder Lee <ryder.lee@mediatek.com>
Acked-by: Sean Wang <sean.wang@kernel.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>