pinctrl: mediatek: add eint support to MT6765 pinctrl driver

Just add eint support to MT6765 pinctrl driver as usual as
happens on the other SoCs.

Signed-off-by: Mars Cheng <mars.cheng@mediatek.com>
Signed-off-by: Sean Wang <sean.wang@mediatek.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>