Changes:
* drive_uninit() wants a DriveInfo now.
* drive_uninit() also calls bdrv_delete(),
so callers don't need to do that.
* drive_uninit() calls are moved over to the ->exit()
callbacks, destroy_bdrvs() is zapped.
* setting bdrv->private is not needed any more as the
only user (destroy_bdrvs) is gone.
* usb-storage needs no drive_uninit, scsi-disk will
handle that.
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com> Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>