Update git submodules

Update git submodules

* Update docs/submodules/sfc from branch 'master'
  - Adding Dimitris as a committer

    Dimitris has been helping a lot in the 2 previous releases. This last release
    has proven that he is essential to the project adding features like
    multi-installer support and helping debug SFC in both APEX and xci. That's why
    I think he should become committer in the OPNFV-SFC project

    Change-Id: I9fced455db635864cc1ef3523bc6b2bc78d54c5f
    Signed-off-by: Manuel Buil <mbuil@suse.com>