pdc202xx_new: move PIO programming code to pdcnew_set_pio_mode()

* Move PIO programming code from pdcnew_set_mode() to pdcnew_set_pio_mode().

* Rename pdcnew_set_mode() to pdcnew_set_dma_mode().

There should be no functionality changes caused by this patch.

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