Issue FEAT_CHANGE notification when features are changed by
netdev_update_features().  This will allow changes made by extra constraints
on e.g. MTU change to be properly propagated like changes via ethtool.
Signed-off-by: NMichał Mirosław <mirq-linux@rere.qmqm.pl>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>