libata: PIIX3 support

This I believe completes the PIIX range of support for libata

This adds the table entries needed for the PIIX3, both a new PCI
identifier and a new mode list. It also fixes an erroneous access to PCI
configuration 0x48 on non UDMA capable chips.

Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>