Update git submodules

Update git submodules

* Update docs/submodules/vswitchperf from branch 'master'
  - Merge "trex: fix Trex makefile"
  - trex: fix Trex makefile

    Trex makefile was fix to checkout correct commit ID.
    Add trex repo folder to .gitignore file.

    JIRA: VSPERF-528

    Change-Id: Icd0406eaf088b88c28d90cf8a7dd9e1fa53a6f3b
    Signed-off-by: Martin Goldammer <martin.goldammer6@gmail.com>
    Reviewed-by: Martin Klozik <martinx.klozik@intel.com>
    Reviewed-by: Al Morton <acmorton@att.com>
    Reviewed-by: Christian Trautman <ctrautma@redhat.com>
    Reviewed-by: Trevor Cooper <trevor.cooper@intel.com>