cfg80211: add wrappers for registered_device_ops

This will allow adding central tracing like in mac80211.

Signed-off-by: Hila Gonen <hila.gonen@intel.com>
Reviewed-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Reviewed-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>