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