pyloxi: fix of_wc_bmap_t for OF 1.2+

This field changed semantics, so the LOXI type probably should change too.
diff --git a/py_gen/codegen.py b/py_gen/codegen.py
index e552d61..d6d8b32 100644
--- a/py_gen/codegen.py
+++ b/py_gen/codegen.py
@@ -217,4 +217,4 @@
     util.render_template(out, 'pp.py')
 
 def generate_util(out, name, version):
-    util.render_template(out, 'util.py')
+    util.render_template(out, 'util.py', version=version)