Printrboard G2 support (#13116)

Marlin/src/core/boards.h

@@ -222,6 +222,12 @@
 #define BOARD_ARCHIM1          1591   // UltiMachine Archim1 (with DRV8825 drivers)
 #define BOARD_ARCHIM2          1592   // UltiMachine Archim2 (with TMC2130 drivers)
 #define BOARD_ALLIGATOR        1602   // Alligator Board R2
+
+//
+// SAM3X8C ARM Cortex M3
+//
+
+#define BOARD_PRINTRBOARD_G2   1620   // PRINTRBOARD G2
 #define BOARD_ADSK             1610   // Arduino DUE Shield Kit (ADSK)
 
 //