Update git submodules

* Update docs/submodules/yardstick from branch 'stable/euphrates'
  - Addition of NSB Prox test documentation of vPE and LW-AFTR test cases

    YARDSTICK-840

    NSB Prox test documentation of vPE and LW-AFTR test cases documenation.

    Change-Id: Ic6da6546faf0494fdee71962a515083e6e10a410
    Signed-off-by: Daniel Martin Buckley <daniel.m.buckley@intel.com>
    (cherry picked from commit db6083d91499521bf3a486623e985cc3b1703524)

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index d49ecc8..2292505 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit d49ecc822d24bcd53675c0186a178ac8adc894c0
+Subproject commit 2292505e94d2225569d743c9e31063ba6bff03f8