nfp: flower: ensure deletion of old offloaded MACs

When a potential tunnel end point goes down then its MAC address should
not be matchable on the NFP.

Implement a delete message for offloaded MACs and call this on net device
down. While at it, remove the actions on register and unregister netdev
events. A MAC should only be offloaded if the device is up. Note that the
netdev notifier will replay any notifications for UP devices on
registration so NFP can still offload ports that exist before the driver
is loaded. Similarly, devices need to go down before they can be
unregistered so removal of offloaded MACs is only required on down events.

Signed-off-by: John Hurley <john.hurley@netronome.com>
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>