These fields were used to manually handle IO requests that weren't aligned
to a sector boundary before this feature was supported by the block API.

Once the block API changed to support byte-aligned IO requests, the macio
controller was switched over to use it in commit be1e3439 but these fields
were accidentally left behind. Remove them, including the initialisation
in DBDMA_init().

Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>