Update git submodules

* Update docs/submodules/vswitchperf from branch 'master'
  - Fix for multi-stream configuration

    The multistream configuration is not passed to the remote host where the traffic generator (MoonGen) runs.

    Change-Id: I3e9862553b5b064272f3bfffb788c06ebd3740ca
    Signed-off-by: Marco Varlese <marco.varlese@suse.com>

diff --git a/docs/submodules/vswitchperf b/docs/submodules/vswitchperf
index 0f6f846..26ec31c 160000 (submodule)
--- a/docs/submodules/vswitchperf
+++ b/docs/submodules/vswitchperf
@@ -1 +1 @@
-Subproject commit 0f6f846cfb0f38f16baf1192e3f3dc5effb517bb
+Subproject commit 26ec31cb51f6c7fb9ef89cc437b69167be98b4bf