ekf: add range finder "faulty" status

When delclared faulty, the range finder cannot be used anymore

src/modules/ekf2/EKF/common.h

@@ -490,6 +490,7 @@ union filter_control_status_u {
 		uint32_t synthetic_mag_z : 1; ///< 25 - true when we are using a synthesized measurement for the magnetometer Z component
 		uint32_t vehicle_at_rest : 1; ///< 26 - true when the vehicle is at rest
 		uint32_t gps_yaw_fault : 1; ///< 27 - true when the GNSS heading has been declared faulty and is no longer being used
+		uint32_t rng_fault : 1; ///< 28 - true when the range finder has been declared faulty and is no longer being used
 	} flags;
 	uint32_t value;
 };

src/modules/ekf2/EKF/sensor_range_finder.cpp

@@ -62,7 +62,7 @@ void SensorRangeFinder::updateValidity(uint64_t current_time_us)
 {
 	updateDtDataLpf(current_time_us);
 
-	if (isSampleOutOfDate(current_time_us) || !isDataContinuous()) {
+	if (_is_faulty || isSampleOutOfDate(current_time_us) || !isDataContinuous()) {
 		_is_sample_valid = false;
 		_is_regularly_sending_data = false;
 		return;

src/modules/ekf2/EKF/sensor_range_finder.hpp

@@ -106,6 +106,8 @@ public:
 	float getValidMinVal() const { return _rng_valid_min_val; }
 	float getValidMaxVal() const { return _rng_valid_max_val; }
 
+	void setFaulty() { _is_faulty = true; }
+
 private:
 	void updateSensorToEarthRotation(const matrix::Dcmf &R_to_earth);
 
@@ -123,6 +125,7 @@ private:
 	bool _is_sample_valid{};	///< true if range finder sample retrieved from buffer is valid
 	bool _is_regularly_sending_data{false}; ///< true if the interval between two samples is less than the maximum expected interval
 	uint64_t _time_last_valid_us{};	///< time the last range finder measurement was ready (uSec)
+	bool _is_faulty{false};         ///< the sensor should not be used anymore
 
 	/*
 	 * Stuck check