board: nuvoton: use an event to replace last_stage_init()

Add a new event which handles this function refer to commit
("91caa3bb89b1 event: Use an event to replace last_stage_init()")

Signed-off-by: Michael Chang <zhang971090220@gmail.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
6 files changed