popup : fix create scroller bug when list item add.

Summary:
data-> scr = scroller object
data-> scroll = scrollable flag.
in _list_add function, when scroller object is not created, do _create_scroller.
 if (!sd->scroll) _create_scroller(obj);
must change to
 if (!sd->scr) _create_scroller(obj);

@fix

Reviewers: jaehwan, id213sin, cedric, raster, singh.amitesh

Reviewed By: singh.amitesh

Subscribers: herb, jpeg

Differential Revision: https://phab.enlightenment.org/D3866

src/lib/elementary/elc_popup.c

@@ -687,7 +687,7 @@ _list_add(Evas_Object *obj)
 {
    ELM_POPUP_DATA_GET(obj, sd);
 
-   if (!sd->scroll)
+   if (!sd->scr)
      _create_scroller(obj);
    //Box
    sd->box = elm_box_add(sd->scr);