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>
diff --git a/board/nuvoton/common/uart.h b/board/nuvoton/common/uart.h
index 9cc8952..fc8ec47 100644
--- a/board/nuvoton/common/uart.h
+++ b/board/nuvoton/common/uart.h
@@ -6,6 +6,6 @@
 #ifndef _NUVOTON_UART_H
 #define _NUVOTON_UART_H
 
-void board_set_console(void);
+int board_set_console(void);
 
 #endif /* _NUVOTON_COMMON_H */