serialization: Add support for std::set

xyz.openbmc_project.Common.Threshold interface has added a property of
type `set` (which sdbusplus maps to a std::set). Add Cereal support for
serializing std::set.

Tested:
Build that was earlier failing for the Threshold type now passes.

Change-Id: Ic22bfe94f902dc7fc4ffd0ef0fcdfa6565620f60
Signed-off-by: Santosh Puranik <santosh.puranik.ibm@gmail.com>
diff --git a/gen_serialization.mako.hpp b/gen_serialization.mako.hpp
index 036b131..f7e19fc 100644
--- a/gen_serialization.mako.hpp
+++ b/gen_serialization.mako.hpp
@@ -2,11 +2,13 @@
 ## into the rendered file; feel free to edit this file.
 // This file was auto generated.  Do not edit.
 
+#include "config.h"
+
+#include <cereal/types/map.hpp>
+#include <cereal/types/set.hpp>
 #include <cereal/types/string.hpp>
 #include <cereal/types/tuple.hpp>
 #include <cereal/types/vector.hpp>
-#include <cereal/types/map.hpp>
-#include "config.h"
 % for iface in interfaces:
 #include <${iface.header()}>
 % endfor