dpaa2-switch: cleanup the egress flood of an unused FDB

In case a DPAA2 switch interface joins a bridge, the FDB used on the
port will be changed to the one associated with the bridge. What this
means exactly is that any VLAN installed on the port will need to be
removed and then installed back so that it points to the new FDB.

Once this is done, the previous FDB will become unused (no VLAN to
point to it). Even though no traffic will reach this FDB, it's best to
just cleanup the state of the FDB by zeroing its egress flood domain.

Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>