mlxsw: spectrum: Enable L3 interfaces on top of bridge devices

As with the previously introduced L3 interfaces, listen to 'inetaddr'
notifications sent for bridges devices configured on top of the port
netdevs and create / destroy router interfaces (RIFs) accordingly.
This also includes VLAN devices configured on top of the VLAN-aware
bridge.

The RIFs will be destroyed either when the last IP address is removed or
when the underlying FID is is destroyed.

Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>