network: bridge: add support for IFLA_BRPORT_LOCKED

network: bridge: add support for IFLA_BRPORT_LOCKED

Since linux commit a21d9a670d81103db7f788de1a4a4a6e4b891a0b ("net:
bridge: Add support for bridge port in locked mode"), included since
v5.18,  it is possible to set bridge ports to locked.

Locked ports do not learn automatically, and discard any traffic from
unknown source MACs. To allow traffic, the userspace authenticator is
expected to create fdb entries for authenticated hosts.

Add support to systemd-network for setting the new attribute for bridge
ports.