SKR 1.3 sensorless endstops hack (#16659)

Marlin/src/pins/lpc1768/pins_BTT_SKR_V1_3.h

 
 /**
  * Limit Switches
- *
- * For Stallguard homing to max swap the min / max pins so
- * the MAX physical connectors can be used for other things.
  */
-#if X_HOME_DIR == -1 || !X_STALL_SENSITIVITY
+#if X_HOME_DIR > 0 && X_STALL_SENSITIVITY && !defined(USE_XMAX_PLUG)
+  // For StallGuard homing to MAX swap the MIN / MAX pins
+  // so the MAX physical connectors may be used for other things.
+  #define X_MIN_PIN          P1_28   // X_MAX (free)
+  #define X_MAX_PIN          P1_29   // X_MIN
+#else                                // else, non-endstop is free and appears in M43 output
   #define X_MIN_PIN          P1_29   // X_MIN
   #define X_MAX_PIN          P1_28   // X_MAX
-#else
-  #define X_MIN_PIN          P1_28   // X_MAX
-  #define X_MAX_PIN          P1_29   // X_MIN
 #endif
 
-#if Y_HOME_DIR == -1 || !Y_STALL_SENSITIVITY
+#if Y_HOME_DIR > 0 && Y_STALL_SENSITIVITY && !defined(USE_YMAX_PLUG)
+  #define Y_MIN_PIN          P1_26   // Y_MAX (free)
+  #define Y_MAX_PIN          P1_27   // Y_MIN
+#else
   #define Y_MIN_PIN          P1_27   // Y_MIN
   #define Y_MAX_PIN          P1_26   // Y_MAX
-#else
-  #define Y_MIN_PIN          P1_26   // Y_MAX
-  #define Y_MAX_PIN          P1_27   // Y_MIN
 #endif
 
-#if Z_HOME_DIR == -1 || !Z_STALL_SENSITIVITY
+#if Z_HOME_DIR > 0 && Z_STALL_SENSITIVITY && !defined(USE_ZMAX_PLUG)
+  #define Z_MIN_PIN          P1_24   // Z_MAX (free)
+  #define Z_MAX_PIN          P1_25   // Z_MIN
+#else
   #define Z_MIN_PIN          P1_25   // Z_MIN
   #define Z_MAX_PIN          P1_24   // Z_MAX
-#else
-  #define Z_MIN_PIN          P1_24   // Z_MAX
-  #define Z_MAX_PIN          P1_25   // Z_MIN
 #endif
 
 #define ONBOARD_ENDSTOPPULLUPS     // Board has built-in pullups