Add support for MeCreator2 (#12017)

Marlin/src/core/boards.h

 #define BOARD_TRIGORILLA_13     343   // TriGorilla Anycubic version 1.3 based on RAMPS EFB
 #define BOARD_TRIGORILLA_14     443   // TriGorilla Anycubic version 1.4 based on RAMPS EFB
 #define BOARD_RAMPS_ENDER_4     243   // Creality: Ender-4, CR-8
-#define BOARD_GT2560_V3         76    // Geeetech A10
 #define BOARD_FYSETC_F6_13      541   // Fysetc F6
 
 //
 #define BOARD_SCOOVO_X9H        321   // abee Scoovo X9H
 #define BOARD_GT2560_REV_A      74    // Geeetech GT2560 Rev. A
 #define BOARD_GT2560_REV_A_PLUS 75    // Geeetech GT2560 Rev. A+ (with auto level probe)
+#define BOARD_GT2560_V3         76    // Geeetech GT2560 Rev B for A10(M/D)
+#define BOARD_GT2560_V3_MC2     73    // Geeetech GT2560 Rev B for Mecreator2																		   																	 
 #define BOARD_EINSTART_S        666   // Einstart retrofit
 
 //

Marlin/src/pins/pins.h

   #include "pins_TRIGORILLA_14.h"     // ATmega2560                                 env:megaatmega2560
 #elif MB(RAMPS_ENDER_4)
   #include "pins_RAMPS_ENDER_4.h"     // ATmega2560                                 env:megaatmega2560
-#elif MB(GT2560_V3)
-  #include "pins_GT2560_V3.h"         // ATmega2560                                 env:megaatmega2560
-#elif MB(FYSETC_F6_13)
-  #include "pins_FYSETC_F6_13.h"      // ATmega2560                                 env:megaatmega2560
 
 //
 // Other ATmega1280, ATmega2560
   #include "pins_GT2560_REV_A.h"      // ATmega1280, ATmega2560                     env:megaatmega1280 env:megaatmega2560
 #elif MB(GT2560_REV_A_PLUS)
   #include "pins_GT2560_REV_A_PLUS.h" // ATmega1280, ATmega2560                     env:megaatmega1280 env:megaatmega2560
+#elif MB(GT2560_V3)
+  #include "pins_GT2560_V3.h"         // ATmega2560                                 env:megaatmega2560
+#elif MB(GT2560_V3_MC2)
+  #include "pins_GT2560_V3_MC2.h"     // ATmega2560                                 env:megaatmega2560
 #elif MB(EINSTART_S)
   #include "pins_EINSTART-S.h"        // ATmega1280, ATmega2560                     env:megaatmega1280 env:megaatmega2560
 

Marlin/src/pins/pins_GT2560_V3_MC2.h

+/**
+ * Marlin 3D Printer Firmware
+ * Copyright (C) 2016 MarlinFirmware [https://github.com/MarlinFirmware/Marlin]
+ *
+ * Based on Sprinter and grbl.
+ * Copyright (C) 2011 Camiel Gubbels / Erik van der Zalm
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+/*****************************************************************
+ * GT2560 V3.0 pin assignment (for Mecreator 2)
+ *****************************************************************/
+
+#define BOARD_NAME "GT2560 V3.0 (MC2)"
+
+#include "pins_GT2560_V3.h"
+
+#undef X_MIN_PIN
+#define X_MIN_PIN          22
+
+#undef X_MAX_PIN
+#define X_MAX_PIN          24
+
+#undef Y_MIN_PIN
+#define Y_MIN_PIN          26
+
+#undef Y_MAX_PIN
+#define Y_MAX_PIN          28