Update git submodules

* Update docs/submodules/yardstick from branch 'stable/euphrates'
  - Merge "load_images.sh: Add missing ssh_options" into stable/euphrates
  - load_images.sh: Add missing ssh_options

    Empty ssh_options led to ssh login failure, which stopped the whole
    script.

    Change-Id: I8374a30a02b14d04eb0f623a0c58d7ebed77a589
    Signed-off-by: Alexandru Avadanii <Alexandru.Avadanii@enea.com>
    (cherry picked from commit 77c7d358bc6a61e2a5c24c6056cc3e40561f27c7)

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index 898cd51..66fe3f8 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit 898cd51e6f55a32e882fba86f5dac32e6d89b1ca
+Subproject commit 66fe3f812a21ffc4da4404d7461505daac5d345e