net: dsa: lantiq_gswip: support bridge FDB entries on the CPU port

net: dsa: lantiq_gswip: support bridge FDB entries on the CPU port

Currently, the driver takes the bridge from dsa_port_bridge_dev_get(),
which only works for user ports. This is why it has to ignore FDB
entries installed on the CPU port.

Commit c26933639b54 ("net: dsa: request drivers to perform FDB
isolation") introduced the possibility of getting the originating bridge
from the passed dsa_db argument, so let's do that instead. This way, we
can act on the local FDB entries coming from the bridge.

Note that we do not expect FDB events for the DSA_DB_PORT database,
because this driver doesn't fulfill the dsa_switch_supports_uc_filtering()
requirements. So we can just return -EOPNOTSUPP and expect it will never
be triggered.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: Daniel Golle <daniel@makrotopia.org>
Link: https://patch.msgid.link/ed9d847c0356f0fec81422bdad9ebdcc6a59da79.1760566491.git.daniel@makrotopia.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>