One or two ancient drives predated the cable spec and didn't sent the
valid bits for the field. I had hoped to leave this out of libata as a
piece of historical annoyance but a recent CD drive shows the same bug so
we have to import support for it.

Same concept as Bartlomiej's changes old IDE except that as we have
centralised blacklists we can avoid keeping another private table of stuff
Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>