net: dsa: Include BR_PORT_LOCKED in the list of synced brport flags

Ensures that the DSA switch driver gets notified of changes to the
BR_PORT_LOCKED flag as well, for the case when a DSA port joins or
leaves a LAG that is a bridge port.

Signed-off-by: Hans Schultz <schultz.hans+netdev@gmail.com>
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>