The ATA specifications require checks on certain flags before assuming
the validity of other data. Go through the methods and correct those
needing extra checks. Also note limits on ata_id_major_version with
respect to ATA-1 and ATA-2. Correct the 32bit PIO check.

Wants to sit in -mm for a bit in case of a screwup on my part that I
didn't hit on the test drives and also in case someone, somewhere has
a drive that gets it wrong.
Signed-off-by: NAlan Cox <alan@redhat.com>
Signed-off-by: NJeff Garzik <jeff@garzik.org>