Some quick backport bits from the libata PATA work to fix things found in
the sis driver.  The piix driver needs some fixes too but those are way to
large and need someone working on old IDE with time to do them.

This patch fixes the case where random bits get loaded into SIS timing
registers according to the description of the correct behaviour from
Vojtech Pavlik.  It also adds the SiS5517 ATA16 chipset which is not
currently supported by the driver.  Thanks to Conrad Harriss for loaning me
the machine with the 5517 chipset.
Signed-off-by: Alan Cox <alan@redhat.com>
Acked-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>