AP_BoardConfig: fixed AUAV21 board ID to not overlap with VRBrain boards

libraries/AP_BoardConfig/AP_BoardConfig.cpp

@@ -154,7 +154,7 @@ const AP_Param::GroupInfo AP_BoardConfig::var_info[] = {
     // @Param: TYPE
     // @DisplayName: Board type
     // @Description: This allows selection of a PX4 or VRBRAIN board type. If set to zero then the board type is auto-detected (PX4)
-    // @Values: 0:AUTO,1:PX4V1,2:Pixhawk,3:Pixhawk2,4:Pixracer,5:PixhawkMini,6:Pixhawk2Slim,7:VRBrain 5.1,8:VRBrain 5.2,9:VR Micro Brain 5.1,10:VR Micro Brain 5.2,11:VRBrain Core 1.0,12:VRBrain 5.4
+    // @Values: 0:AUTO,1:PX4V1,2:Pixhawk,3:Pixhawk2,4:Pixracer,5:PixhawkMini,6:Pixhawk2Slim,7:VRBrain 5.1,8:VRBrain 5.2,9:VR Micro Brain 5.1,10:VR Micro Brain 5.2,11:VRBrain Core 1.0,12:VRBrain 5.4,20:AUAV2.1
     // @RebootRequired: True
     // @User: Advanced
     AP_GROUPINFO("TYPE", 9, AP_BoardConfig, px4.board_type, BOARD_TYPE_DEFAULT),

libraries/AP_BoardConfig/AP_BoardConfig.h

@@ -46,7 +46,7 @@ public:
         PX4_BOARD_PIXRACER = 4,
         PX4_BOARD_PHMINI   = 5,
         PX4_BOARD_PH2SLIM  = 6,
-        PX4_BOARD_AUAV21   = 7,
+        PX4_BOARD_AUAV21   = 20,
         PX4_BOARD_OLDDRIVERS = 100,
 #endif
 #if CONFIG_HAL_BOARD == HAL_BOARD_VRBRAIN