AP_NavEKF2: use get_distance_NE instead of location_diff

libraries/AP_NavEKF2/AP_NavEKF2_Measurements.cpp

@@ -531,7 +531,7 @@ void NavEKF2_core::readGpsData()
 
             // convert GPS measurements to local NED and save to buffer to be fused later if we have a valid origin
             if (validOrigin) {
-                gpsDataNew.pos = location_diff(EKF_origin, gpsloc);
+                gpsDataNew.pos = EKF_origin.get_distance_NE(gpsloc);
                 gpsDataNew.hgt = (float)((double)0.01 * (double)gpsloc.alt - ekfGpsRefHgt);
                 storedGPS.push(gpsDataNew);
                 // declare GPS available for use

libraries/AP_NavEKF2/AP_NavEKF2_Outputs.cpp

@@ -252,7 +252,7 @@ bool NavEKF2_core::getPosNE(Vector2f &posNE) const
             if ((AP::gps().status() >= AP_GPS::GPS_OK_FIX_2D)) {
                 // If the origin has been set and we have GPS, then return the GPS position relative to the origin
                 const struct Location &gpsloc = AP::gps().location();
-                Vector2f tempPosNE = location_diff(EKF_origin, gpsloc);
+                const Vector2f tempPosNE = EKF_origin.get_distance_NE(gpsloc);
                 posNE.x = tempPosNE.x;
                 posNE.y = tempPosNE.y;
                 return false;