Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Docs: add yardstick gui descrption in userguide

    Change-Id: I09bc55e296d2c641f10819972ec0d48a289432b8
    Signed-off-by: JingLu5 <lvjing5@huawei.com>

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index 1b059e4..cca247f 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit 1b059e41e553247bda0168d6b40eb67b56e7b56e
+Subproject commit cca247fe1bc5b98192609ecb61148ae0667cb345