Update git submodules

* Update docs/submodules/releng from branch 'master'
  - Merge "Added license metadata to specify Apache-2.0"
  - Added license metadata to specify Apache-2.0

    Change-Id: Id2e6b148f896eee5122339e501c8604e74ef774c
    Signed-off-by: rpaik <rpaik@linuxfoundation.org>

diff --git a/docs/submodules/releng b/docs/submodules/releng
index e449925..51875bd 160000 (submodule)
--- a/docs/submodules/releng
+++ b/docs/submodules/releng
@@ -1 +1 @@
-Subproject commit e44992530bcd032ba7f5754d233fee03f523c680
+Subproject commit 51875bd0ad16530ad5179e32859b132ea1e1a534