pinctrl: mediatek: Add Pinctrl/GPIO/EINT driver for mt2701

Add mt2701 support using mediatek common pinctrl driver.
MT2701 have some special pins need an extra setting register
than other ICs, so adding this support to common code.

Signed-off-by: Biao Huang <biao.huang@mediatek.com>
Acked-by: Yingjoe Chen <yingjoe.chen@mediatek.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>