commander: monitor GPS validity and EKF2 dead reckoning

- ekf2: expose dead reckoning as control status flags
 - commander:
    - add GPS validity check
    - in AUTO MISSION if dependent on GPS then a loss of GPS will

src/modules/ekf2/EKF/airspeed_fusion.cpp

@@ -58,7 +58,7 @@ void Ekf::fuseAirspeed()
 			       math::constrain(_airspeed_sample_delayed.eas2tas, 0.9f, 10.0f));
 
 	// determine if we need the airspeed fusion to correct states other than wind
-	const bool update_wind_only = !_is_wind_dead_reckoning;
+	const bool update_wind_only = !_control_status.flags.wind_dead_reckoning;
 
 	// Intermediate variables
 	const float HK0 = vn - vwn;