Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Merge "Adding vfw scale-up test with ixia as tg"
  - Adding vfw scale-up test with ixia as tg

    Change-Id: I4f476d16dd11a12f5ffa9047af78d2236a4fbbc2
    Signed-off-by: Deepak S <deepak.s@linux.intel.com>

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index 6808c51..f3f9196 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit 6808c51c5fcd8e437b162fe10d2cc0a37223ccac
+Subproject commit f3f9196cd76a46f6b5fbf1dc06533d6bc65991c3