Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Merge "improve logging, clear using print"
  - improve logging, clear using print

    Change-Id: I744353f631cf1771d75f750543e8612f81be71ee
    Signed-off-by: rexlee8776 <limingjiang@huawei.com>

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index 449ce23..b3c51ed 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit 449ce236523fef4b494573b74d90f91d0afdb280
+Subproject commit b3c51ed384eb538f1458512dbab312c53d6de134