* Merge ->atapi_{in,out}put_bytes and ->ata_{in,out}put_data methods
  into new ->{in,out}put_data methods which take number of bytes to
  transfer as an argument and always do padding.

While at it:

* Use 'hwif' or 'drive->hwif' instead of 'HWIF(drive)'.

There should be no functional changes caused by this patch (all users
of ->ata_{in,out}put_data methods were using multiply-of-4 word counts).
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>