power: abx500_chargalg: Remove deprecated create_singlethread_workqueue

alloc_ordered_workqueue() with WQ_MEM_RECLAIM set replaces
deprecated create_singlethread_workqueue(). This is the identity
conversion.

The workqueue "chargalg_wq" is used for running the charging algorithm.
It has multiple workitems viz &di->chargalg_periodic_work,
&di->chargalg_wd_work, &di->chargalg_work per abx500_chargalg, which
require ordering. It has been identity converted.

Also, WQ_MEM_RECLAIM has been set to ensure forward progress under
memory pressure.

Signed-off-by: Bhaktipriya Shridhar <bhaktipriya96@gmail.com>
Signed-off-by: Sebastian Reichel <sre@kernel.org>