Rover: fix build with new mavlink repo

APMrover2/system.pde

@@ -191,7 +191,6 @@ static void init_ardupilot()
 
 	//mavlink_system.sysid = MAV_SYSTEM_ID;				// Using g.sysid_this_mav
 	mavlink_system.compid = 1;	//MAV_COMP_ID_IMU;   // We do not check for comp id
-	mavlink_system.type = MAV_TYPE_GROUND_ROVER;
 
     rc_override_active = hal.rcin->set_overrides(rc_override, 8);