libata: remove no longer needed pata_qdi driver

QDI65x0 controllers are fully supported by pata_legacy driver
so remove no longer needed pata_qdi driver.

Leave PATA_QDI config option for compatibility reasons and teach
pata_legacy to preserve the old behavior of pata_qdi driver.

Acked-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>