Update git submodules

* Update docs/submodules/ipv6 from branch 'stable/fraser'
  - Final Release Notes 6.0.0. Ready

    Change-Id: I188faadc70ed54090f9202974498e3a74effde35
    Signed-off-by: Bin Hu <bh526r@att.com>
    (cherry picked from commit 9b5b71cae4ca1d83688395aa4e58466b23e96acb)

  - Revise ODL Gap Analysis of IPv6 N-S Support

    Change-Id: I263dd18c5f50dd707e2154612f820eae81c00633
    Signed-off-by: Bin Hu <bh526r@att.com>
    (cherry picked from commit dfcc0745ef76e684593c8284f9dcb81cca2f7959)

diff --git a/docs/submodules/ipv6 b/docs/submodules/ipv6
index dfcc074..8d92071 160000 (submodule)
--- a/docs/submodules/ipv6
+++ b/docs/submodules/ipv6
@@ -1 +1 @@
-Subproject commit dfcc0745ef76e684593c8284f9dcb81cca2f7959
+Subproject commit 8d92071b644ac9e45208feca41b6d45f008ec9a0