Update git submodules

* Update docs/submodules/usecase-ui.git from branch 'master'
  to 15235e6fc3bf84bc14d56e6604e2a76cfcc07db8
  - docs: add README.md and CHANGELOG.md
    
    Change-Id: Ifa1c1059ab85e72e62c41529a337d7efc0ce042e
    Issue-ID: USECASEUI-306
    Signed-off-by: cyuamber <xuranyjy@chinamobile.com>
    
diff --git a/docs/submodules/usecase-ui.git b/docs/submodules/usecase-ui.git
index fbd2d66..15235e6 160000
--- a/docs/submodules/usecase-ui.git
+++ b/docs/submodules/usecase-ui.git
@@ -1 +1 @@
-Subproject commit fbd2d6628f9d639895ef45b4a100ed00cecfd342
+Subproject commit 15235e6fc3bf84bc14d56e6604e2a76cfcc07db8