Update git submodules

* Update docs/submodules/qtip from branch 'master'
  - Fix bug in ``qtip/scripts/quickstart.sh``

    - line 29: error: command not found

    Change-Id: I0256ae89aaf4938b883cfae72d30f73d43b1da76
    Signed-off-by: Yujun Zhang <zhang.yujunz@zte.com.cn>

diff --git a/docs/submodules/qtip b/docs/submodules/qtip
index 583d718..c57f521 160000 (submodule)
--- a/docs/submodules/qtip
+++ b/docs/submodules/qtip
@@ -1 +1 @@
-Subproject commit 583d7181b15ae6f8d6319c36bad6fd043f47c89f
+Subproject commit c57f521a767737605d8e739de0e470a96923def0