clang-format: Sort using statements

Make using order consistent where used. There aren't any in this
project, but this should be used more widely by openbmc projects.

Change-Id: I5e2395f480cbf76e1d3e006b1ab648da5aa39aec
Signed-off-by: Adriana Kobylak <anoo@us.ibm.com>
diff --git a/cpp-style-and-conventions.md b/cpp-style-and-conventions.md
index be365ec..03f3167 100644
--- a/cpp-style-and-conventions.md
+++ b/cpp-style-and-conventions.md
@@ -248,6 +248,7 @@
 PointerAlignment: Left
 ReflowComments:  true
 SortIncludes:    true
+SortUsingDeclarations: true
 SpaceAfterCStyleCast: false
 SpaceBeforeAssignmentOperators: true
 SpaceBeforeParens: ControlStatements