Use the following facts:

- rq->nr_sectors should now be always equal to (non-zero)
  rq->hard_nr_sectors for fs requests

- REQ_TYPE_ATA_PC requests have never bio attached to them

- rq->hard_nr_sectors == 0 for REQ_TYPE_ATA_PC requests

- DMA is used only for fs, pc and REQ_TYPE_ATA_PC requests

- 'uptodate' is ignored for pc requests ('rc == 0' case)

and use the common completion path also for DMA requests.

There should be no functional changes caused by this patch

Cc: Borislav Petkov <petkovbb@gmail.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>