net: cleanup vlan_features setting in register_netdev

vlan_features contains features inherited from underlying device.
NETIF_SOFT_FEATURES are not inherited but belong to the vlan device
itself (ensured in vlan_dev_fix_features()).

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