elm_spinner: sync button visibility

elm_spinner: sync button visibility

This patch is related to accessibility.
The button of spinner has visible state, even though spinner does not show.

The efl_ui_clock could use spiner internally.
Usually it adds 5 spinners and does not show some of them according to
the time format.

We tried to apply following patch, but it is not acceptable.
- elm_datetime_format_set(dd->datetime, "%d/%b/%Y %I:%M %p");
+ elm_datetime_format_set(dd->datetime, "%I:%M %p");

- elm_datetime_format_set(dd->datetime, "%d/%b/%Y %H:%M");
+ elm_datetime_format_set(dd->datetime, "%H:%M");

Change-Id: If7182e669271931b54b3266f79252c87f4cd6bdf