pinctrl: mediatek: make MediaTek pinctrl v2 driver ready for buidling loadable module

pinctrl: mediatek: make MediaTek pinctrl v2 driver ready for buidling loadable module

In the future we want to be able to build the MediaTek pinctrl driver,
based on paris, as kernel module. This patch allows pinctrl-paris.c, the
external interrupt controller mtk-eint.c, and pinctrl-mtk-common-v2.c to
be loadable as module.

Signed-off-by: Sean Wang <sean.wang@mediatek.com>
Signed-off-by: Light Hsieh <light.hsieh@mediatek.com>
Reviewed-by: Matthias Brugger <matthias.bgg@gmail.com>
Link: https://lore.kernel.org/r/9feeb04805e5a406fe22a92e3f280abda39ddda4.1586289920.git.sean.wang@mediatek.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>