Fix GT2560 A+ servo pin

Marlin/src/pins/pins_GT2560_REV_A.h

   #error "Oops!  Make sure you have 'Arduino Mega' selected from the 'Tools -> Boards' menu."
 #endif
 
-#define BOARD_NAME           "GT2560 Rev.A"
+#ifndef BOARD_NAME
+  #define BOARD_NAME "GT2560 Rev.A"
+#endif
 #define DEFAULT_MACHINE_NAME "Prusa i3 Pro B"
+
 //
 // Limit Switches
 //

Marlin/src/pins/pins_GT2560_REV_A_PLUS.h

  * Geeetech GT2560 Revision A+ board pin assignments
  */
 
-#include "pins_GT2560_REV_A.h"
+#define BOARD_NAME "GT2560 Rev.A+"
 
-#undef BOARD_NAME
-#define BOARD_NAME  "GT2560 Rev.A+"
+#include "pins_GT2560_REV_A.h"
 
 #if ENABLED(BLTOUCH)
-  #define SERVO0_PIN  32
-#else
   #define SERVO0_PIN  11
+#else
+  #define SERVO0_PIN  32
 #endif