NUVOTON: CAN: Fix undeclared function gpio_set

ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]

Author: ccli8

targets/TARGET_NUVOTON/TARGET_M261/can_api.c

@@ -23,6 +23,7 @@
  #include "cmsis.h"
  #include "pinmap.h"
  #include "PeripheralPins.h"
+ #include "gpio_api.h"
  #include "nu_modutil.h"
  #include "nu_miscutil.h"
  #include "nu_bitutil.h"

targets/TARGET_NUVOTON/TARGET_M451/can_api.c

@@ -23,6 +23,7 @@
  #include "cmsis.h"
  #include "pinmap.h"
  #include "PeripheralPins.h"
+ #include "gpio_api.h"
  #include "nu_modutil.h"
  #include "nu_miscutil.h"
  #include "nu_bitutil.h"

targets/TARGET_NUVOTON/TARGET_NUC472/can_api.c

@@ -23,6 +23,7 @@
  #include "cmsis.h"
  #include "pinmap.h"
  #include "PeripheralPins.h"
+ #include "gpio_api.h"
  #include "nu_modutil.h"
  #include "nu_miscutil.h"
  #include "nu_bitutil.h"