AP_BoardConfig: added AUAV21 board type

unfortunately this uses the same sensor types as the PHMini, which
means we can't auto-detect the difference between them.

libraries/AP_BoardConfig/AP_BoardConfig.h

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

libraries/AP_BoardConfig/px4_drivers.cpp

@@ -322,6 +322,7 @@ void AP_BoardConfig::px4_setup_drivers(void)
     case PX4_BOARD_PIXHAWK2:
     case PX4_BOARD_PIXRACER:
     case PX4_BOARD_PHMINI:
+    case PX4_BOARD_AUAV21:
     case PX4_BOARD_PH2SLIM:
         break;
     default: