ide-cris: add PIO autotune fallback to ->ide_dma_check

Since ide-cris allows separate PIO and DMA timings, and ide-cris always sets
->autotune this change shouldn't have any other effect than bringing ide-cris
driver in-line with other host drivers wrt ->ide_dma_check implementation.

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