ionic: export features for vlans to use

Set up vlan_features for use by any vlans above us.

Fixes: beead698

 ("ionic: Add the basic NDO callbacks for netdev support")
Signed-off-by: Shannon Nelson <snelson@pensando.io>
Acked-by: Jonathan Toppins <jtoppins@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>