ata: libata-core: remove ata_bus_probe()

Remove ata_bus_probe() as it is unused.

Also, remove references to ata_bus_probe and port_disable in
Documentation/driver-api/libata.rst, as neither exist anymore.

Signed-off-by: Niklas Cassel <niklas.cassel@wdc.com>
Reviewed-by: John Garry <john.g.garry@oracle.com>
Reviewed-by: Jason Yan <yanaijie@huawei.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Damien Le Moal <dlemoal@kernel.org>