control: Add missing zone.hpp include to functor.hpp

Found this to be missing for the forward declaration of the Zone class
while testing the creation of trigger objects from JSON.

Change-Id: I3c5d19889c9eb1738add1ee9f4870f7d8e386ba0
Signed-off-by: Matthew Barth <msbarth@us.ibm.com>
diff --git a/control/functor.hpp b/control/functor.hpp
index 658c76a..f24d219 100644
--- a/control/functor.hpp
+++ b/control/functor.hpp
@@ -2,6 +2,7 @@
 
 #include "sdbusplus.hpp"
 #include "types.hpp"
+#include "zone.hpp"
 
 #include <phosphor-logging/log.hpp>