From: Carsten Haustein <chaus@cs.uni-potsdam.de>

A bug in function piix_config_drive_xfer_rate() allows a call of
hwif->ide_dma_on(drive) without prior call of piix_config_drive_for_dma().
This results in harddisk configured for UDMA (default?) whereas the highest
DMA mode supported by PIIX3 is MWORD2.

This bug is supposed to be present in any 2.6.x kernel release and any
2.4.x kernel release since 2.4.21.

bart: this should also fix the same bug for PIIXa and PIIXb

Fixes bugzilla bug #3473.
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>