pata_sl82c105: remove un-needed code paths

Remove the DMA setup function. As pointed out by Sergey we set the actual
DMA clock timing in set_dmamode so we don't actually need to do anything
with it at set up time, but just leave the PIO timings loaded.

Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>