atiixp: DMA setup fixes

* Fix handling of unsupported/invalid modes in atiixp_set_dma_mode().

* ATI controllers allow separate PIO and DMA timings so remove programming
  of PIO modes from atiixp_set_dma_mode().  Also remove no longer needed
  atiixp_dma_2_pio() helper.

* SWDMA timings are not programmed by atiixp_set_dma_mode() and if SWDMA
  mode is chosen atiixp_dma_host_on() erroneously enables UDMA, just disable
  support for SWDMA modes for now.

* Enable support for MWDMA0 mode.

* Bump driver version.

Acked-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>