Update git submodules

* Update docs/submodules/samplevnf from branch 'stable/gambia'
  - Add Gambia release notes

    Change-Id: Ide712ee94254b506a0ad88c95a7e01b789f99d49
    Signed-off-by: Deepak S <deepak.s@linux.intel.com>

diff --git a/docs/submodules/samplevnf b/docs/submodules/samplevnf
index 5d0595c..bffb52a 160000 (submodule)
--- a/docs/submodules/samplevnf
+++ b/docs/submodules/samplevnf
@@ -1 +1 @@
-Subproject commit 5d0595c955eb37af44b68098b6fd4f33f18e7755
+Subproject commit bffb52abba29f2b9c9e1288cfbfbace54d62eb9e