Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Merge "fix invalid chracters in ansible scripts"
  - fix invalid chracters in ansible scripts

    Change-Id: I3d1a491e4c0f0554a861d9bb24fbd0ac94835759
    Signed-off-by: Deepak S <deepak.s@linux.intel.com>

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index 679133f..b4819ac 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit 679133f49500ff929c5a8597ab37c3d1fcd72ee9
+Subproject commit b4819ac38d60f0565ba310621ea9518d6c4ba280