soc: npcx: replace Nuvoton NPCX series definitions in the npcx drivers

Replace Nuvoton NPCX series definitions with new Kconfig definitions in
the npcx drivers. The benefit of this approach is that we won't touch
the npcx driver sources again during introducing a new npcx series next
time.

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