Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Merge "Added multi-port testcases for vFW"
  - Added multi-port testcases for vFW

    Change-Id: I6cf8675c83fc081dd22ae7896e63ff7725ed3c13
    Signed-off-by: Deepak S <deepak.s@linux.intel.com>
    Signed-off-by: Ross Brattain <ross.b.brattain@intel.com>

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index 3d38334..7e2cf50 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit 3d3833448a5f46840d38d4f4c72a7bd37139ca0b
+Subproject commit 7e2cf50af684b10779430f52c01b378f7c796012