APM_OBC: updates for new AP_Param API

libraries/APM_OBC/APM_OBC.h

@@ -35,6 +35,8 @@ public:
 	// Constructor
 	APM_OBC(void)
 	{
+		AP_Param::setup_object_defaults(this, var_info);
+
 		_last_heartbeat_pin = -1;
 		_last_manual_pin = -1;
 		_state = STATE_PREFLIGHT;