Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Merge "[workaround] Disable gui for aarch64"
  - [workaround] Disable gui for aarch64

    Currently the aarch64 yardstick image doesn't build because phantomsj and bower
    don't install properly. Temporarily disable gui for aarch64 only so we can
    still get the other updates.

    JIRA: ARMBAND-391

    Change-Id: I64f892641c7bdb1cb3a65b210f71b093878b1688
    Signed-off-by: Cristina Pauna <cristina.pauna@enea.com>

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index 8c470c7..a562d50 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit 8c470c7ae7ffccc06a7dada3eda9689d50d6ba89
+Subproject commit a562d505bf1549b41e93ecae4d8461f31851aa20