ekf2 selector fix SITL lockstep

- ekf2 selector don't register lockstep until first attitude publication
 - sensors module register lockstep component
 - enable multi-EKF2 in SITL

src/modules/sensors/sensors.cpp

@@ -178,6 +178,7 @@ private:
 
 	VehicleIMU      *_vehicle_imu_list[MAX_SENSOR_COUNT] {};
 
+	int _lockstep_component{-1};
 
 	/**
 	 * Update our local parameter cache.
@@ -297,6 +298,8 @@ Sensors::~Sensors()
 	}
 
 	perf_free(_loop_perf);
+
+	px4_lockstep_unregister_component(_lockstep_component);
 }
 
 bool Sensors::init()
@@ -639,6 +642,12 @@ void Sensors::Run()
 		parameter_update_poll();
 	}
 
+	if (_lockstep_component == -1) {
+		_lockstep_component = px4_lockstep_register_component();
+	}
+
+	px4_lockstep_progress(_lockstep_component);
+
 	perf_end(_loop_perf);
 }