Update git submodules

Update git submodules

* Update docs/submodules/vswitchperf from branch 'master'
  - gitignore: Ignore non vsperf files

    .gitignore was updated to ignore following files:
    * VPP project directory
    * l2fwd binary files
    * tags

    JIRA: VSPERF-529

    Change-Id: Idc10eae7b14c72a863f3473e02cbdc7c47d31b41
    Signed-off-by: Cian Ferriter <cian.ferriter@intel.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: Sridhar Rao <sridhar.rao@spirent.com>
    Reviewed-by: Trevor Cooper <trevor.cooper@intel.com>