Callbacks are empty now, so remove them.

Also, remove the call to ap->ops->port_start() in ata_sas_port_init(),
as this would otherwise cause a NULL pointer dereference, now when the
callback is gone.
Signed-off-by: Hannes Reinecke <hare@suse.de>
[niklas: remove the call to ap->ops->port_start() in ata_sas_port_init()]
Signed-off-by: Niklas Cassel <niklas.cassel@wdc.com>
Reviewed-by: Jason Yan <yanaijie@huawei.com>
Reviewed-by: John Garry <john.g.garry@oracle.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Damien Le Moal <dlemoal@kernel.org>