net: Fix vlan_features propagation

Fix VLAN features propagation for devices which change vlan_features.
For this to work, driver needs to make sure netdev_features_changed()
gets called after the change (it is e.g. after ndo_set_features()).

Side effect is that a user might request features that will never
be enabled on a VLAN device.

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