Update git submodules

* Update docs/submodules/availability from branch 'master'
  - Local Documentation Builds

        This adds configuration for performing local documentation builds
        with the following simple command:

        tox -e docs

    added index.rst so that docs build succsesfully

    Change-Id: If257dec8d76d3ecf7d75e6cb4771dd9617db7fa4
    Signed-off-by: Aric Gardner <agardner@linuxfoundation.org>

diff --git a/docs/submodules/availability b/docs/submodules/availability
index d0c0673..15a4164 160000 (submodule)
--- a/docs/submodules/availability
+++ b/docs/submodules/availability
@@ -1 +1 @@
-Subproject commit d0c0673873f9cfd1752f25d58b760bb2bf51a930
+Subproject commit 15a4164a7995aca710d0016ee9e2e1f7a508044b