whci: Remove deprecated create_singlethread_workqueue

alloc_ordered_workqueue replaces the deprecated
create_singlethread_workqueue.

The workqueue "workqueue" has multiple workitems which may require
ordering. Hence, a dedicated ordered workqueue has been used.
Since the workqueue is not being used on a memory reclaim path,
WQ_MEM_RECLAIM has not been set.

Signed-off-by: Bhaktipriya Shridhar <bhaktipriya96@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>