Copter: simplify home distance and bearing calculation

ArduCopter/navigation.cpp

@@ -14,9 +14,7 @@ void Copter::run_nav_updates(void)
 uint32_t Copter::home_distance()
 {
     if (position_ok()) {
-        const Vector3f home = pv_location_to_vector(ahrs.get_home());
-        const Vector3f curr = inertial_nav.get_position();
-        _home_distance = get_horizontal_distance_cm(curr, home);
+        _home_distance = get_distance_cm(current_loc, ahrs.get_home());
     }
     return _home_distance;
 }
@@ -25,9 +23,7 @@ uint32_t Copter::home_distance()
 int32_t Copter::home_bearing()
 {
     if (position_ok()) {
-        const Vector3f home = pv_location_to_vector(ahrs.get_home());
-        const Vector3f curr = inertial_nav.get_position();
-        _home_bearing = get_bearing_cd(curr,home);
+        _home_bearing = get_bearing_cd(current_loc, ahrs.get_home());
     }
     return _home_bearing;
 }