Add has_broadcast_disable flag to type-data and generic config_init.

This allows us to remove the ksz8081 config_init callback.

Note that ksz8021_config_init is kept for now due to a95a18afe4c8
("phy/micrel: KSZ8031RNL RMII clock reconfiguration bug").
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>