M303 thermal runaway protection

Marlin/src/module/temperature.h

@@ -429,7 +429,7 @@ class Temperature {
      * Perform auto-tuning for hotend or bed in response to M303
      */
     #if HAS_PID_HEATING
-      static void PID_autotune(float temp, int hotend, int ncycles, bool set_result=false);
+      static void PID_autotune(const float temp, const int8_t hotend, const int8_t ncycles, const bool set_result=false);
     #endif
 
     /**