MAINTAINERS: update maintainers for hal_nuvoton

The nuvoton HAL module is for the Numicro platform, not NPCX. Update the
list of maintainers accordingly.

Link: https://github.com/zephyrproject-rtos/zephyr/issues/49678#issuecomment-1233666614


Signed-off-by: Fabio Baltieri <fabiobaltieri@google.com>