Update git submodules

* Update docs/submodules/ipv6 from branch 'master'
  - Fix a comma ","

    Change-Id: Icaddfaa8e291ed90362a8a138c84a5bb8ed7b2e0
    Signed-off-by: BIN HU <bin.hu@att.com>

diff --git a/docs/submodules/ipv6 b/docs/submodules/ipv6
index 5b5d796..a5373e3 160000 (submodule)
--- a/docs/submodules/ipv6
+++ b/docs/submodules/ipv6
@@ -1 +1 @@
-Subproject commit 5b5d796db2cd130bdc843038bf471ebe7dc3325a
+Subproject commit a5373e3e990b940619ba9d07246fe106c57edde5