Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Merge "Supporting user config task parameters in GUI"
  - Supporting user config task parameters in GUI

    JIRA: YARDSTICK-981

    We need to add function to enable user to config task parameters in GUI.
    The way to config must be more friendly.

    Change-Id: I8746149084f1d554b48ed392f2fef4748e279dfb
    Signed-off-by: chenjiankun <chenjiankun1@huawei.com>

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index 8fe2c9f..a6a54f1 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit 8fe2c9fd13783fc5aa0f3b488274b5f892f2f260
+Subproject commit a6a54f115cb55a4cf91df24e9b894f89b232dae8