bridge: call netdev_sw_port_stp_update when bridge port STP status changes

To notify switch driver of change in STP state of bridge port, add new
.ndo op and provide switchdev wrapper func to call ndo op. Use it in bridge
code then.

Signed-off-by: Scott Feldman <sfeldma@gmail.com>
Signed-off-by: Jiri Pirko <jiri@resnulli.us>
Signed-off-by: Andy Gospodarek <gospo@cumulusnetworks.com>
Acked-by: Thomas Graf <tgraf@suug.ch>
Acked-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>