On the road to kill all prims, llc_prim_data bits the dust, now
the core queues the data directly and takes care of the conf semantics,
i.e. waking up the upper layer when the confirmation arrives. Maybe I'll
have to put more info on skb->cb for conf and ind, but for PF_LLC this is
enough for now. Have to check NetBEUI tho. But we can always add back
removed features, better than having features that nobody uses :-)