pinctrl: mediatek: use generic EINT register maps for each SoC

So far, EINT on each SoC all used exactly identical register map and thus
it's better that we apply generic register map already supported in EINT
library and stop copy-n-pasting the same data block and filling into its
platform data.

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