pinctrl: mediatek: Add get_direction support.

Since Linux gpio framework return 0 for output, 1 for input.
But HW use 0 stands for input, and 1 stands for output.
So use negative to correct it.

And gpio_chip.get is used to get input value, no need to get
output value, so removing it.

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