🧑‍💻 Add AXIS_COLLISION to catch broken parameters

Marlin/src/core/types.h

@@ -64,6 +64,8 @@ struct IF<true, L, R> { typedef L type; };
   #define GANG_ITEM_E(N)
 #endif
 
+#define AXIS_COLLISION(L) (AXIS4_NAME == L || AXIS5_NAME == L || AXIS6_NAME == L)
+
 //
 // Enumerated axis indices
 //

Marlin/src/gcode/config/M200-M205.cpp

@@ -253,7 +253,7 @@ void GcodeSuite::M205() {
   if (parser.seenval('S')) planner.settings.min_feedrate_mm_s = parser.value_linear_units();
   if (parser.seenval('T')) planner.settings.min_travel_feedrate_mm_s = parser.value_linear_units();
   #if HAS_JUNCTION_DEVIATION
-    #if HAS_CLASSIC_JERK && (AXIS4_NAME == 'J' || AXIS5_NAME == 'J' || AXIS6_NAME == 'J')
+    #if HAS_CLASSIC_JERK && AXIS_COLLISION('J')
       #error "Can't set_max_jerk for 'J' axis because 'J' is used for Junction Deviation."
     #endif
     if (parser.seenval('J')) {