libata: Spot bridge chips

If we have a PATA cable with a SATA drive on it then we've found a
bridge and we can flip the cable type. This fixes some cable detect
problems with SATA bridges on chipsets and misdetected cable types.

In theory cable detection and mode limiting is needed if you put a
SATA/PATA bridge on a 40 wire cable, but I see no way to deal with
that other than to point out its not a good idea anyway.

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