drivers: pinctrl: npcx: add initial pin-controller driver

This CL is the initial version for npcx pinctrl driver and introduces
pinctrl nodes for both IO-pads and peripheral devices for each npcx
series. Users can set pin configuration via these nodes in the board
layout DT file. It also wraps all configurations related to pin-muxing
in pinctrl_soc.h. Regarding the other pin properties, we will implement
them later.

Signed-off-by: Mulin Chao <mlchao@nuvoton.com>