Update git submodules

* Update docs/submodules/apex from branch 'stable/danube'
  - Merge "Updates the real time kvm kernel from 4.4.6-rt14 to 4.4.50-rt62." into stable/danube
  - Updates the real time kvm kernel from 4.4.6-rt14 to 4.4.50-rt62.

    Change-Id: Iee42eb2533fe8c8336113613ab578aa56abb37fb
    Signed-off-by: davidjchou <david.j.chou@intel.com>
    (cherry picked from commit e6e035be520fd2f1021f524f11a9f19cd70523a2)

diff --git a/docs/submodules/apex b/docs/submodules/apex
index c6b4b82..d94215f 160000 (submodule)
--- a/docs/submodules/apex
+++ b/docs/submodules/apex
@@ -1 +1 @@
-Subproject commit c6b4b82f7f9d13721ae141b570221a20b53117ce
+Subproject commit d94215f00bafd38466e3eaa7d2724bb8c42e0fe3