Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Merge "Remove unnecessary function definition in IxLoadTrafficGen"
  - Remove unnecessary function definition in IxLoadTrafficGen

    Removed call to 'instantiate' base class in IxLoadTrafficGen.

    JIRA: YARDSTICK-894

    Change-Id: I0ebee1f5e0f22cfd3a67eaac8accc67ecd35ad0c
    Signed-off-by: Rodolfo Alonso Hernandez <rodolfo.alonso.hernandez@intel.com>

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index c191b30..b1225db 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit c191b305790b4528868725db82d1af6c0d95e22b
+Subproject commit b1225dbbc53723741757810d3283258f157e20e4