update .clang-format

Added the header inclusion order to the .clang-format file generated
these changes.

Change-Id: I4f51a20f469de431ee6a5ba78e3f4da39c980fab
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/src/event_serialize.hpp b/src/event_serialize.hpp
index f052845..d331950 100644
--- a/src/event_serialize.hpp
+++ b/src/event_serialize.hpp
@@ -1,9 +1,11 @@
 #pragma once
 
-#include <experimental/filesystem>
-#include "event_entry.hpp"
 #include "config.h"
 
+#include "event_entry.hpp"
+
+#include <experimental/filesystem>
+
 namespace phosphor
 {
 namespace events