types: fixup header

Fixup types.hpp to include the message header that provides the types
used.

Change-Id: If75a3288aa9a1ecd8313d50caf8d93f76e1ce06d
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/types.hpp b/types.hpp
index e874960..d4f656c 100644
--- a/types.hpp
+++ b/types.hpp
@@ -1,7 +1,7 @@
 #pragma once
 
 #include <map>
-#include <sdbusplus/server.hpp>
+#include <sdbusplus/message.hpp>
 #include <string>
 
 namespace ipmi