Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Merge "Fix up formatting on devguide"
  - Fix up formatting on devguide

    * Change the notation used for heading levels and
      add a key at the top of the file.
    * Wrap lines at 80 characters.
    * Highlight keywords

    Change-Id: Ic6e7194270bbffb3ddaf688c774b632287b0c201
    JIRA: YARDSTICK-1253
    Signed-off-by: Emma Foley <emma.l.foley@intel.com>

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index c1552c7..e8eca1a 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit c1552c7dc4c08892fae93a2f5a420f2195745e32
+Subproject commit e8eca1a5678754b54d5c83c28ba2f7cd38d85880