net: dsa: mv88e6xxx: remove addresses when a port leaves a VLAN

Add a new _mv88e6xxx_atu_move function to prepare the ATU data register
for the move operation. The ports vector will contain the source port
and destination port of the Move operation. If the destination port is
0xF, the MAC addresses mapped to the source port are removed for the
address database(s).

Then add a _mv88e6xxx_atu_remove wrapper to remove the MAC addresses
from a VLAN database that are mapped to a given port, when it leaves it.

Signed-off-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Signed-off-by: David S. Miller <davem@davemloft.net>