Update git submodules

Update git submodules

* Update docs/submodules/releng from branch 'master'
  - Merge "Update repository with new location of XCI"
  - Update repository with new location of XCI

    With the releng-xci code moving to it's own repository, the Jenkins jobs
    need to be modify to clone the correct repo and point at the right
    paths:

     * The git repo is changed to 'releng-xci'
     * The cloned directory is changed to '$WORKSPACE/releng-xci'
     * References to the 'prototypes' directory path have been removed

    Change-Id: Ia1d2ad0a2fb6cc9d1848356edf448b92ab67b017
    Signed-off-by: Trevor Bramwell <tbramwell@linuxfoundation.org>