On reboot the loop in device_shutdown gets confused by these partially
initialized devices and goes into an infinite loop. Therefore unregister
and disable these devices.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
[bart: remove leftover hwif->present clearing + update patch description]
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>