Change Marlin debug flag names to fix conflicts (#12340)

In reference to #11000

Marlin/src/gcode/bedlevel/abl/G29.cpp

@@ -157,7 +157,7 @@ G29_TYPE GcodeSuite::G29() {
   // G29 Q is also available if debugging
   #if ENABLED(DEBUG_LEVELING_FEATURE)
     const uint8_t old_debug_flags = marlin_debug_flags;
-    if (seenQ) marlin_debug_flags |= DEBUG_LEVELING;
+    if (seenQ) marlin_debug_flags |= MARLIN_DEBUG_LEVELING;
     if (DEBUGGING(LEVELING)) {
       DEBUG_POS(">>> G29", current_position);
       log_machine_info();