Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - KVMFORNFV: Grafana config for Packet Forwarding test cases.

    This patch is used for adding configuration file to opnfv grafana
    dashboard for kvmfornfv packet forwarding test cases as a part of
    daily job.

    Change-Id: If2f06d2c01a7f6863ae1aa25942c3197856d895b
    Signed-off-by: Gundarapu Kalyan Reddy <reddyx.gundarapu@intel.com>

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index 49844d2..2240fcc 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit 49844d2d7bf43eda8adda6fc6dd48357b736aa39
+Subproject commit 2240fcc201fa9665e42e92c29e201cb62490acfa