Update git submodules

* Update docs/submodules/yardstick from branch 'stable/danube'
  - increase line length to 99

    When line length is 79 I have to spend too much
    time manually wrapping my code into unreadable junk

    I can't use expressive tuple unpacking and I start
    shortening variables and other bad tricks to decrease
    the line length.

    We have too many levels of indent to manage with 79

    class:
      def:
         if:
             for:
                  etc.

    Change-Id: Ib2ce9cf887f9880c46815822c8d0e1a7806e53ca
    Signed-off-by: Ross Brattain <ross.b.brattain@intel.com>
    (cherry picked from commit 98fdb2810a7010edf0f12af0ed5d706df2af615c)

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index d609aa7..75be9a1 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit d609aa7438e543354debfe86ab9d34a0e6402eda
+Subproject commit 75be9a172539d9e45f113001ed0b3daeb06e0e1c