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/sideslip_fusion.cpp

@@ -72,7 +72,7 @@ void Ekf::fuseSideslip()
 		const float R_BETA = sq(_params.beta_noise); // observation noise variance
 
 		// determine if we need the sideslip fusion to correct states other than wind
-		bool update_wind_only = !_is_wind_dead_reckoning;
+		bool update_wind_only = !_control_status.flags.wind_dead_reckoning;
 
 		// Intermediate Values
 		const float HK0 = vn - vwn;