pinctrl: nuvoton: modify NPCM7xx pin configuration function

Modify GPIO direction setting in pin configuration function by using
generic GPIO functions to set the GPIO direction instead of direct
access to the GPIO direction register.

Signed-off-by: Tomer Maimon <tmaimon77@gmail.com>
Tested-by: Kun Yi <kunyi@google.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>