java_gen: added ability to define metadata for enums

added metadata PortSpeed to OFPortFeatures
diff --git a/java_gen/java_type.py b/java_gen/java_type.py
index e7f2201..0844686 100644
--- a/java_gen/java_type.py
+++ b/java_gen/java_type.py
@@ -305,6 +305,7 @@
 meter_features = JType("OFMeterFeatures")\
         .op(read="OFMeterFeaturesVer$version.READER.readFrom(bb)", write="$name.writeTo(bb)")
 
+port_speed = JType("PortSpeed")
 boolean = JType("boolean")
 
 generic_t = JType("T")