[EFL] Remove useless assignment code in _ewk_tiled_backing_store_zoom_set_internal.

[EFL] Remove useless assignment code in _ewk_tiled_backing_store_zoom_set_internal.
https://bugs.webkit.org/show_bug.cgi?id=68594

As the 1st assignment of local variable bx in _ewk_tiled_backing_store_zoom_set_internal
isn't effective at all, this patch just removes it.

Patch by KwangHyuk Kim <hyuki.kim@samsung.com> on 2011-09-28
Reviewed by Ryosuke Niwa.

* ewk/ewk_tiled_backing_store.c:
(_ewk_tiled_backing_store_zoom_set_internal):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@96291 268f45cc-cd09-0410-ab3c-d52691b4dbfc