Add support for RUMBA thermocouple add on

Marlin/temperature.cpp

@@ -571,6 +571,12 @@ static void updateTemperaturesFromRawValues()
 
 void tp_init()
 {
+#if (MOTHERBOARD == 80) && ((TEMP_SENSOR_0==-1)||(TEMP_SENSOR_1==-1)||(TEMP_SENSOR_2==-1)||(TEMP_SENSOR_BED==-1))
+  //disable RUMBA JTAG in case the thermocouple extension is plugged on top of JTAG connector
+  MCUCR=(1<<JTD); 
+  MCUCR=(1<<JTD);
+#endif
+  
   // Finish init of mult extruder arrays 
   for(int e = 0; e < EXTRUDERS; e++) {
     // populate with the first value