Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Merge "apexlake: speed unittest, mock time.sleep"
  - apexlake: speed unittest, mock time.sleep

    Change-Id: I40cbcd1963bbb2481282c34b2360c77a5bef109b
    Signed-off-by: Ross Brattain <ross.b.brattain@intel.com>

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index 93df930..8d85e42 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit 93df930fbd7e8f0f4a7868be469ab7b1fa2b3c47
+Subproject commit 8d85e42443d8ebea23c90d82ae649716ecc713cb