Update security string to 2016-09-07 to platform and CTS for September
  respin

Change-Id: I0f753925387a19fa055efd08ce026ef98431ef03
diff --git a/core/version_defaults.mk b/core/version_defaults.mk
index be5f861..74ae18b 100644
--- a/core/version_defaults.mk
+++ b/core/version_defaults.mk
@@ -68,7 +68,7 @@
   # Can be an arbitrary string, but must be a single word.
   #
   # If there is no $PLATFORM_SECURITY_PATCH set, keep it empty.
-  PLATFORM_SECURITY_PATCH := 2016-09-05
+  PLATFORM_SECURITY_PATCH := 2016-09-07
 endif
 
 ifeq "" "$(PLATFORM_BASE_OS)"