Fix compilation issue with decouple test

Thanks @Seiler270 for pointing out

src/ArduinoDUE/Repetier/Extruder.cpp

@@ -406,8 +406,10 @@ void TemperatureController::waitForTargetTemperature()
 fast8_t TemperatureController::errorState() {
 	if(isSensorDefect())
 		return 1;
+#if FEATURE_DECOUPLE_TEST
 	if(isSensorDecoupled())
 		return 2;
+#endif
 #if EXTRUDER_JAM_CONTROL
 	if(isFilamentChange())
 		return 6;

src/ArduinoDUE/Repetier/Extruder.h

@@ -83,9 +83,11 @@ public:
     {
         return flags & TEMPERATURE_CONTROLLER_FLAG_DECOUPLE_FULL;
     }
+#endif
 	inline void removeErrorStates() {
         flags &= ~(TEMPERATURE_CONTROLLER_FLAG_ALARM | TEMPERATURE_CONTROLLER_FLAG_SENSDEFECT | TEMPERATURE_CONTROLLER_FLAG_SENSDECOUPLED);
 	}
+#if FEATURE_DECOUPLE_TEST
     inline bool isDecoupleFullOrHold()
     {
         return flags & (TEMPERATURE_CONTROLLER_FLAG_DECOUPLE_FULL | TEMPERATURE_CONTROLLER_FLAG_DECOUPLE_HOLD);