driver: intc: npcx: replace miwu offset macros with inline functions.

This CL replaces macros for miwu multi-registers' offset with internal
inline functions. This CL also uses soc series definitions to
distinguish the layout of miwu multi-registers between different npcx
series.

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