Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Merge "Adjust timeouts for installing requrements"
  - Adjust timeouts for installing requrements

    The time it takes to install the the requirements is different on the 2 build
    servers we have for aarch64: on build4 it takes ~12min, on pod5 it takes <10min.
    So the timeouts need to be adjusted again to bigger values to cover both servers.

    JIRA: ARMBAND-391

    Change-Id: Idd8f07e6f54d64a6cfaee0753ecd8efd141ff615
    Signed-off-by: Cristina Pauna <cristina.pauna@enea.com>

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index 29b6e11..6988c5a 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit 29b6e112447ef79827de96414ec6d82c14ae9a37
+Subproject commit 6988c5a09a649988225b8ab674d52aab5df6f9a7