drivers: PS/2: npcx: Replace device_get_binding with DEVICE_DT_GET

Replace device_get_binding() with DEVICE_DT_GET to obtain the PS/2
controller and clock control device objects. It helps to improve the
efficiency for driver initialization as DEVICE_DT_GET is processed
at the link time rather than run time.

Signed-off-by: Jun Lin <CHLin56@nuvoton.com>