Update git submodules

* Update docs/submodules/armband from branch 'stable/euphrates'
  - Update the armband documentation

    Since the x86 and arm documentation for Fuel is now common, I just
    copied the documentation made in fuel project as is.

    JIRA: ARMBAND-293

    Change-Id: I6bfd26c9c911829ae556db0388bb16310d8280ba
    Signed-off-by: Cristina Pauna <cristina.pauna@enea.com>
    (cherry picked from commit 0a53afff6289fc0e2a0af8c4f6efc9e565d0cdae)

diff --git a/docs/submodules/armband b/docs/submodules/armband
index 13b071a..a1e421d 160000 (submodule)
--- a/docs/submodules/armband
+++ b/docs/submodules/armband
@@ -1 +1 @@
-Subproject commit 13b071a86f5c552be17f12ae90ae73b94c1dc741
+Subproject commit a1e421da5e038224f6950c3c15444d98d67f4782