Fix an unused var warning

Marlin/src/HAL/LPC1768/HAL.cpp

@@ -67,9 +67,7 @@ int16_t PARSED_PIN_INDEX(const char code, const int16_t dval) {
   return ind > -1 ? ind : dval;
 }
 
-void flashFirmware(int16_t value) {
-  NVIC_SystemReset();
-}
+void flashFirmware(const int16_t) { NVIC_SystemReset(); }
 
 void HAL_clear_reset_source(void) {
   #if ENABLED(USE_WATCHDOG)

Marlin/src/HAL/LPC1768/HAL.h

@@ -195,7 +195,7 @@ int16_t PARSED_PIN_INDEX(const char code, const int16_t dval);
 void HAL_idletask();
 
 #define PLATFORM_M997_SUPPORT
-void flashFirmware(int16_t value);
+void flashFirmware(const int16_t);
 
 /**
  * set_pwm_frequency

Marlin/src/HAL/STM32/HAL.cpp

@@ -133,6 +133,6 @@ void HAL_adc_start_conversion(const uint8_t adc_pin) { HAL_adc_result = analogRe
 
 uint16_t HAL_adc_get_result() { return HAL_adc_result; }
 
-void flashFirmware(int16_t) { NVIC_SystemReset(); }
+void flashFirmware(const int16_t) { NVIC_SystemReset(); }
 
 #endif // ARDUINO_ARCH_STM32 && !STM32GENERIC

Marlin/src/HAL/STM32/HAL.h

@@ -223,4 +223,4 @@ uint16_t HAL_adc_get_result();
 #define PARSED_PIN_INDEX(code, dval) parser.intval(code, dval)
 
 #define PLATFORM_M997_SUPPORT
-void flashFirmware(int16_t value);
+void flashFirmware(const int16_t);

Marlin/src/HAL/STM32F1/HAL.cpp

@@ -388,6 +388,6 @@ void analogWrite(pin_t pin, int pwm_val8) {
     analogWrite(uint8_t(pin), pwm_val8);
 }
 
-void flashFirmware(int16_t value) { nvic_sys_reset(); }
+void flashFirmware(const int16_t) { nvic_sys_reset(); }
 
 #endif // __STM32F1__

Marlin/src/HAL/STM32F1/HAL.h

@@ -288,4 +288,4 @@ void analogWrite(pin_t pin, int pwm_val8); // PWM only! mul by 257 in maple!?
 #define JTAGSWD_DISABLE() afio_cfg_debug_ports(AFIO_DEBUG_NONE)
 
 #define PLATFORM_M997_SUPPORT
-void flashFirmware(int16_t value);
+void flashFirmware(const int16_t);