docs-rst: admin-guide: add documentation for EDAC

EDAC is part of the Kernel's RAS facilities, with is useful for
system admins to detect errors. So, add it to the admin's guide.

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

Documentation/admin-guide/index.rst

diff --git a/Documentation/admin-guide/index.rst b/Documentation/admin-guide/index.rst
index 2681cbd..8ddae4e 100644
--- a/Documentation/admin-guide/index.rst
+++ b/Documentation/admin-guide/index.rst
@@ -59,6 +59,7 @@
    binfmt-misc
    mono
    java
+   ras
 
 .. only::  subproject and html
 

Documentation/admin-guide/ras.rst

diff --git a/Documentation/edac.txt b/Documentation/admin-guide/ras.rst
similarity index 100%
rename from Documentation/edac.txt
rename to Documentation/admin-guide/ras.rst