distance sensors: Improve variable naming / description

src/modules/ekf2/ekf2_main.cpp

@@ -942,7 +942,7 @@ void Ekf2::run()
 					// check if distance sensor is within working boundaries
 					if (range_finder.min_distance >= range_finder.current_distance ||
 					    range_finder.max_distance <= range_finder.current_distance ||
-					    range_finder.signal_strength == 0) {
+					    range_finder.signal_quality == 0) {
 						// use rng_gnd_clearance if on ground
 						if (_ekf.get_in_air_status()) {
 							range_finder_updated = false;

src/modules/simulator/simulator_mavlink.cpp

@@ -1173,7 +1173,7 @@ int Simulator::publish_distance_topic(mavlink_distance_sensor_t *dist_mavlink)
 	dist.id = dist_mavlink->id;
 	dist.orientation = dist_mavlink->orientation;
 	dist.covariance = dist_mavlink->covariance / 100.0f;
-	dist.signal_strength = -1;
+	dist.signal_quality = -1;
 
 	int dist_multi;
 	orb_publish_auto(ORB_ID(distance_sensor), &_dist_pub, &dist, &dist_multi, ORB_PRIO_HIGH);