util: Fix missing header

Change-Id: Ie4b02a8626195f3147305b6934b763a2090a5f04
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/util.hpp b/util.hpp
index 26067b5..8e579f5 100644
--- a/util.hpp
+++ b/util.hpp
@@ -1,4 +1,5 @@
 #pragma once
+#include <utility>
 
 namespace ipmi_flash
 {