map: fix scale calculation error

Summary:
As the map shows the nearer to the equator,
the scale of the map should be smaller.

In elm_map, the opposite happens because
meters per pixel was miscalculated.
Thus, calculation is corrected
http://wiki.openstreetmap.org/wiki/Slippy_map_tilenames#Resolution_and_Scale
@fix

Reviewers: seoz, woohyun, Hermet

Differential Revision: https://phab.enlightenment.org/D2426

legacy/elementary/src/lib/elm_map.c

@@ -260,7 +260,7 @@ _scale_cb(const Evas_Object *obj EINA_UNUSED,
        (zoom >= (int)(sizeof(_osm_scale_meter) / sizeof(_osm_scale_meter[0])))
       )
      return 0;
-   return _osm_scale_meter[zoom] / cos(lat * ELM_PI / 180.0);
+   return _osm_scale_meter[zoom] * cos(lat * ELM_PI / 180.0);
 }
 
 const Source_Tile src_tiles[] =