efl_ui_animation_view: add document of Efl.Ui.Animation_View_State enum

efl_ui_animation_view: add document of Efl.Ui.Animation_View_State enum

Summary:
This patch will fix mono compiler error.
```
src/bindings/mono/efl_ui_animation_view.eo.cs(2809,13): error CS1591: Warning as
Error: Missing XML comment for publicly visible type or member `Efl.Ui.AnimationViewState'
```

Test Plan: meson setup -Dbindings=mono,cxx

Reviewers: Jaehyun_Cho, SanghyeonLee

Reviewed By: Jaehyun_Cho

Subscribers: cedric, #reviewers, #committers

Tags: #efl

Differential Revision: https://phab.enlightenment.org/D9672

Change-Id: Id083792f1537c60d9204d93c57a556ee519ed3a7