Add pins_RAMPS_13_EFB.h to reduce redundancy

Marlin/pins.h

 #elif MB(RAMPS_OLD)
   #include "pins_RAMPS_OLD.h"
 #elif MB(RAMPS_13_EFB)
-  #define IS_RAMPS_EFB
-  #include "pins_RAMPS_13.h"
+  #include "pins_RAMPS_13_EFB.h"
 #elif MB(RAMPS_13_EEB) || MB(RAMPS_13_EFF) || MB(RAMPS_13_EEF) || MB(RAMPS_13_SF)
   #include "pins_RAMPS_13.h"
 #elif MB(GEN6)

Marlin/pins_AZTEEG_X3.h

  * AZTEEG_X3 Arduino Mega with RAMPS v1.3 pin assignments
  */
 
-#define IS_RAMPS_EFB
-
-#include "pins_RAMPS_13.h"
+#include "pins_RAMPS_13_EFB.h"
 
 //LCD Pins//
 

Marlin/pins_BAM_DICE_DUE.h

  * BAM&DICE Due (Arduino Mega) pin assignments
  */
 
-#define IS_RAMPS_EFB
-
-#include "pins_RAMPS_13.h"
+#include "pins_RAMPS_13_EFB.h"
 
 #undef TEMP_0_PIN
 #undef TEMP_1_PIN

Marlin/pins_FELIX2.h

  * FELIXprinters v2.0/3.0 (RAMPS v1.3) pin assignments
  */
 
-#define IS_RAMPS_EFB
-
-#include "pins_RAMPS_13.h"
+#include "pins_RAMPS_13_EFB.h"
 
 #undef HEATER_1_PIN
 #define HEATER_1_PIN        7 // EXTRUDER 2

Marlin/pins_MKS_BASE.h

  * MKS BASE 1.0 – Arduino Mega2560 with RAMPS v1.4 pin assignments
  */
 
-#define IS_RAMPS_EFB
-
-#include "pins_RAMPS_13.h"
+#include "pins_RAMPS_13_EFB.h"
 
 #undef HEATER_1_PIN
 #define HEATER_1_PIN        7

Marlin/pins_RAMPS_13_EFB.h

+/**
+ * Arduino Mega with RAMPS v1.3 pin assignments
+ *
+ *  RAMPS_13_EFB (Extruder, Fan, Bed)
+ */
+
+#define IS_RAMPS_EFB
+
+#include "pins_RAMPS_13.h"