Use alloc_ordered_workqueue() to allocate the workqueue instead of
create_singlethread_workqueue() since the latter is deprecated and is scheduled
for removal.
There are work items doing related operations that shouldn't be swapped when
queued in a certain order hence preserve the strict execution ordering of a
single threaded (ST) workqueue by switching to alloc_ordered_workqueue().
WQ_MEM_RECLAIM flag is not needed since the worker is not depended
during memory reclaim.