ide: add ->dma_clear method and remove ->dma_timeout one

All custom ->dma_timeout implementations call the generic one thus it is
possible to have only an optional method for resetting DMA engine instead:

* Add ->dma_clear method and convert hpt366, pdc202xx_old and sl82c105
  host drivers to use it.

* Always use ide_dma_timeout() in ide_dma_timeout_retry() and remove
 ->dma_timeout method.

* Make ide_dma_timeout() static.

There should be no functional changes caused by this patch.

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