power: ab8500_fg: Remove deprecated create_singlethread_workqueue

power: ab8500_fg: 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 "fg_wq" is used for running the FG algorithm periodically.
It has been identity converted.

It has multiple work items viz fg_periodic_work, fg_low_bat_work,
fg_reinit_work, fg_work, fg_acc_cur_work and fg_check_hw_failure_work,
which require execution ordering. Hence, a dedicated ordered workqueue
has been used here.

The WQ_MEM_RECLAIM flag has been set to guarantee forward progress under
memory pressure.

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