pinctrl: mediatek: add ies/smt control to common code.

Input enable and smt setting have different register,
modify code to fix it.

Several mediatek soc use similar input enable/smt setting
procedure as mt8173, some soc use generic input enable/smt
setting, some soc has no input enable/smt setting. Adding
common code to handle all those cases, so future soc driver
can use it.

Signed-off-by: Hongzhou Yang <hongzhou.yang@mediatek.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>