Fix utility.cpp for DEBUG_LEVELING_FEATURE

As mentioned in https://github.com/MarlinFirmware/Marlin/issues/9429#issuecomment-385305597

Co-Authored-By: Jack Bradach <jack@bradach.net>

Marlin/src/core/utility.cpp

 
 #endif // EEPROM_SETTINGS
 
-#if ENABLED(ULTRA_LCD)
+#if ENABLED(ULTRA_LCD) || ENABLED(DEBUG_LEVELING_FEATURE)
 
   char conv[8] = { 0 };