pinctrl: mediatek: don't hardcode mode encoding in common code

MT8365 encode the pins mode differently than other
MTK pinctrl drivers that use the PINCTRL_MTK common code.

Add 3 new fields in mtk_pinctrl_devdata in order to store how
pin modes are encoded into the register. At the
same time update all the pinctrl driver that depends on
CONFIG_PINCTRL_MTK.

Signed-off-by: Fabien Parent <fparent@baylibre.com>
Link: https://lore.kernel.org/r/20210519162409.3755679-2-fparent@baylibre.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>