Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Merge "Adding sample trex example"
  - Adding sample trex example

    Change-Id: I3b79d33dba5cc559634122a135ff469f054214fc
    Signed-off-by: Deepak S <deepak.s@linux.intel.com>

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index 8911098..faee281 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit 891109824b93f3dd7b7f553e3561c2cd17495bf6
+Subproject commit faee281ab73e49629265fe66dcfdd456d79be2bc