Update git submodules

* Update docs/submodules/clover from branch 'master'
  - Rename doc to docs

    Change-Id: Iaa83d00704a8d077f8671647b999394eac461482
    Signed-off-by: Yujun Zhang <zhang.yujunz@zte.com.cn>

diff --git a/docs/submodules/clover b/docs/submodules/clover
index 0f1c999..d6d4f31 160000 (submodule)
--- a/docs/submodules/clover
+++ b/docs/submodules/clover
@@ -1 +1 @@
-Subproject commit 0f1c999f546d45e87e0b8e4e7636cf0625dd206a
+Subproject commit d6d4f31e144bc912411baab96ec7cd66b8229800