Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - 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>

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index 816c5b7..77c7d35 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit 816c5b7ad281d792b972609ad08af5986cc22235
+Subproject commit 77c7d358bc6a61e2a5c24c6056cc3e40561f27c7