net: dsa: mv88e6xxx: Flood all traffic classes on standalone ports

In accordance with the comment in dsa_port_bridge_leave, standalone
ports shall be configured to flood all types of traffic. This change
aligns the mv88e6xxx driver with that policy.

Previously a standalone port would initially not egress any unknown
traffic, but after joining and then leaving a bridge, it would.

This does not matter that much since we only ever send FROM_CPUs on
standalone ports, but it seems prudent to make sure that the initial
values match those that are applied after a bridging/unbridging cycle.

Signed-off-by: Tobias Waldekranz <tobias@waldekranz.com>
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>