Update git submodules

* Update docs/submodules/ipv6 from branch 'master'
  - Update images

    Change-Id: If8319f48e254f114a45cc655e6cde6728bb4bb59
    Signed-off-by: BIN HU <bin.hu@att.com>

diff --git a/docs/submodules/ipv6 b/docs/submodules/ipv6
index eeeb529..5b5d796 160000 (submodule)
--- a/docs/submodules/ipv6
+++ b/docs/submodules/ipv6
@@ -1 +1 @@
-Subproject commit eeeb529447a7547e71fde0b7565027e7026a9678
+Subproject commit 5b5d796db2cd130bdc843038bf471ebe7dc3325a