net/mlx4_en: Handle vxlan steering rules for mac address changes

When the device mac address is changed, we must deregister the vxlan
steering rule associated with the previous mac, and register a new
steering rule using the new mac.

Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>