Update git submodules

* Update docs/submodules/vswitchperf from branch 'master'
  - Merge "docs: Update configuration related docs"
  - docs: Update configuration related docs

    A minor update of configuration parameter related documentation.

    Change-Id: Ia97c57162d212541b11ae44aea6eeee8d42f58cb
    Signed-off-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>

diff --git a/docs/submodules/vswitchperf b/docs/submodules/vswitchperf
index ba989f4..67cf875 160000 (submodule)
--- a/docs/submodules/vswitchperf
+++ b/docs/submodules/vswitchperf
@@ -1 +1 @@
-Subproject commit ba989f41bd53f80dbdbade9334661bf5ff1b88e4
+Subproject commit 67cf875fb7548a011aa89799cb814c84513584f5