Add OFPortDesc helper methods
diff --git a/java_gen/templates/custom/OFPortDescVer13.java b/java_gen/templates/custom/OFPortDescVer13.java
new file mode 100644
index 0000000..782a726
--- /dev/null
+++ b/java_gen/templates/custom/OFPortDescVer13.java
@@ -0,0 +1 @@
+//:: include("custom/OFPortDesc.java", msg=msg, has_parent=False)
\ No newline at end of file