ide_hwgroup_t.polling field added.  0 in poll_timeout field
used to indicate inactive polling but because 0 is a valid
jiffy value, though slim, there's a chance that something
weird can happen.
Signed-off-by: Tejun Heo <tj@home-tj.org>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>