net: Call netdev_features_change() from netdev_update_features()

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: Michał Mirosław <mirq-linux@rere.qmqm.pl>
Signed-off-by: David S. Miller <davem@davemloft.net>