Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Merge "pip_license: quick hack script to add license info to requirements.txt"
  - pip_license: quick hack script to add license info to requirements.txt

    Change-Id: Ic41772cb32cd53d405b16880bd43cf89307b4716
    Signed-off-by: Ross Brattain <ross.b.brattain@intel.com>

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index c0af9d0..89fe595 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit c0af9d0667c5653e6a1eba08c8b53664dce865f8
+Subproject commit 89fe59588ec6bf7da5df53cbab61731e476912c3