The original driver doesn't use 66 MHz clock for UDMA33.

[ The alternative solution would be to adjust UDMA33 timings
  for 66 MHz clock but I think that it is safer to stick with
  old & tested behavior for now. ]
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>