efl_ui_widget: skip custom focus parent logic

efl_ui_widget: skip custom focus parent logic

asking for a parent provider only makes sense if we are having a custom
focus parent provider, otherwise this will just result in the normal
parent relation. Not doing this safes us a lot of time that we spent for
nothing in the focus evalulation code.

The gengrid change is needed as the parent provider should be applied
after the constructor is called, otherwise there is no garantee that
shared_win_data is not NULL.

Reviewed-by: Cedric BAIL <cedric.bail@free.fr>
Differential Revision: https://phab.enlightenment.org/D9643