pata_via: add via_fixup()

* Fix via_init_one() to enable clock on 66 MHz devices
  (bug introduced in commit 460f5318 "pata_via: store UDMA masks
   in via_isa_bridges table").

* Factor out common code from via_[re]init_one() to via_fixup().

Acked-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>