Set access as readonly on model field when module is set

(grafted from fd1d0abd2a9256813c654f609b158be3ce3ef9f3)

--HG--
branch : 6.0

trytond/trytond/ir/model.py

@@ -246,6 +246,7 @@ class ModelField(ModelSQL, ModelView):
     access = fields.Boolean(
         "Access",
         states={
+            'readonly': Bool(Eval('module')),
             'invisible': ~Eval('relation'),
             },
         depends=['relation'],