ITE driver/gpio/it8xxx2: add kscan pins gpio driver

Add kscan pins gpio driver for KSI[7:0], KSO[15:0] pins that
they can be configured to gpio mode. These pins registers address,
bit fields and function are different from GPIO group, so I create
a new compatible driver for these pins.

Signed-off-by: Ruibin Chang <Ruibin.Chang@ite.com.tw>