Remove ata_status_t (unused) and atapi_status_t.

While at it:
* replace 'HWIF(drive)' by 'drive->hwif' (or just 'hwif' where possible)
Acked-by: NSergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: NBartlomiej Zolnierkiewicz <bzolnier@gmail.com>