Put driving strength support related functions to pinctrl-mtk-common-v2.c
as these operations might be different by chips and allow different type
of driver to reuse them.
Signed-off-by: Ryder.Lee <ryder.lee@mediatek.com>
Signed-off-by: Sean Wang <sean.wang@mediatek.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>