(SKR 1.3) Assign DIAG pins for homing dir (#15972)

Marlin/src/pins/lpc1768/pins_BTT_SKR.h

@@ -28,16 +28,6 @@
 // Ignore temp readings during development.
 //#define BOGUS_TEMPERATURE_GRACE_PERIOD 2000
 
-//
-// Limit Switches
-//
-#define X_MIN_PIN          P1_29
-#define X_MAX_PIN          P1_28
-#define Y_MIN_PIN          P1_27
-#define Y_MAX_PIN          P1_26
-#define Z_MIN_PIN          P1_25
-#define Z_MAX_PIN          P1_24
-
 //
 // Steppers
 //

Marlin/src/pins/lpc1768/pins_BTT_SKR_V1_1.h

@@ -23,6 +23,17 @@
 
 #define BOARD_INFO_NAME "BIGTREE SKR 1.1"
 
+//
+// Limit Switches
+//
+
+#define X_MIN_PIN          P1_29
+#define X_MAX_PIN          P1_28
+#define Y_MIN_PIN          P1_27
+#define Y_MAX_PIN          P1_26
+#define Z_MIN_PIN          P1_25
+#define Z_MAX_PIN          P1_24
+
 //
 // Steppers
 //

Marlin/src/pins/lpc1768/pins_BTT_SKR_V1_3.h

@@ -23,6 +23,36 @@
 
 #define BOARD_INFO_NAME "BIGTREE SKR 1.3"
 
+/**
+ * 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
+  #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
+  #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
+  #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
+
 //
 // Servos
 //