mlxsw: spectrum_switchdev: Process learned VxLAN FDB entries

Start processing two new entry types in addition to current ones:
* Learned unicast tunnel entry
* Aged-out unicast tunnel entry

In both cases the device reports on a new {MAC, FID, IP address} tuple
that was learned / aged-out. Based on this notification, the driver
instructs the device to add / delete the entry to / from its database.

The driver also makes sure to notify the bridge and VxLAN drivers about
the new entry.

Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Reviewed-by: Petr Machata <petrm@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>