libata: Fix LBA48 on pata_it821x RAID volumes.

[http://lkml.org/lkml/2008/10/18/82]

Signed-off-by: Ondrej Zary <linux@rainbow-software.org>
Acked-by: Alan Cox <alan@redhat.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>