In PCI IDE legacy mode ap->port_no is incorrectly set to zero for
the second port.  Fix it by adding ->hard_port_no to struct ata_probe_ent
and struct ata_port (per Jeff's suggestion) and teaching ata_piix.c
to use it instead of ->port_no.
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>