Fix an unused var warning

Marlin/src/HAL/LPC1768/HAL.cpp

   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

 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

 
 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

 #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

     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

 #define JTAGSWD_DISABLE() afio_cfg_debug_ports(AFIO_DEBUG_NONE)
 
 #define PLATFORM_M997_SUPPORT
-void flashFirmware(int16_t value);
+void flashFirmware(const int16_t);