Update git submodules

* Update docs/submodules/fuel from branch 'master'
  - Merge "docs: add Pod Descriptor Files information"
  - docs: add Pod Descriptor Files information

    Change-Id: I9ca83d2bc42cb15cd37aa3726c02c458fb8a0ea3
    Signed-off-by: Guillermo Herrero <guillermo.herrero@enea.com>

diff --git a/docs/submodules/fuel b/docs/submodules/fuel
index ceedb35..d811bb3 160000 (submodule)
--- a/docs/submodules/fuel
+++ b/docs/submodules/fuel
@@ -1 +1 @@
-Subproject commit ceedb354822eb672fdde6d63d49cbe2f05f29cdb
+Subproject commit d811bb37767e78907bfdaedfc3e7fe723179e728