mlxsw: spectrum: Add missing flood to router port

In case we have a layer 3 interface on top of a bridge (VLAN / FID RIF),
then we should flood the following packet types to the router:

* Broadcast: If DIP is the broadcast address of the interface, then we
need to be able to get it to CPU by trapping it following route lookup.

* Reserved IP multicast (224.0.0.X): Some control packets (e.g. OSPF)
use this range and are trapped in the router block.

Fixes: 99f44bb3 ("mlxsw: spectrum: Enable L3 interfaces on top of bridge devices")
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>