hpt366: merge set_dma_mode() methods

Group the array of pointers to the timing tables with the timing register masks
which allows us to merge HPT36x/HPT37x set_dma_mode() methods into one.

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