Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Merge "Improvie TRex RFC2544 throughput calculation"
  - Improvie TRex RFC2544 throughput calculation

    Improve TRex RFC2544 throughput calculation by using the in/out packets
    instead of using the throughput samples.

    JIRA: YARDSTICK-1387

    Change-Id: I877e901c3226d31c6435a877a2924bb95deb1cf0
    Signed-off-by: Rodolfo Alonso Hernandez <rodolfo.alonso.hernandez@intel.com>

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index 95c0824..5c66661 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit 95c0824278c2e273a3017b7c9b8cf6a026950f74
+Subproject commit 5c6666157a113cae7b5ab52297b8bc482d8484e0