net: dsa: mv88e6xxx: introduce .port_set_policy

Introduce a new .port_set_policy operation to configure a port's
Policy Control List, based on mapping such as DA, SA, Etype and so on.

Models similar to 88E6352 and 88E6390 are supported at the moment.

Signed-off-by: Vivien Didelot <vivien.didelot@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>