Use a special request for serialisation purposes and get rid of the
awkward ide_spin_wait_hwgroup(). This also involves converting the
ide_devset structure so it can be shared by the /proc and the ioctl code.
Signed-off-by: NElias Oltmanns <eo@nebensachen.de>
[bart: use rq->cmd[] directly]
Signed-off-by: NBartlomiej Zolnierkiewicz <bzolnier@gmail.com>