net: bridge: fdb: add support for flush filtering based on ifindex and vlan

Add support for fdb flush filtering based on destination ifindex and
vlan id. The ifindex must either match a port's device ifindex or the
bridge's. The vlan support is trivial since it's already validated by
rtnl_fdb_del, we just need to fill it in.

Signed-off-by: Nikolay Aleksandrov <razor@blackwall.org>
Signed-off-by: David S. Miller <davem@davemloft.net>