ACPI: scan: replace use of system_unbound_wq with system_dfl_wq

Currently if a user enqueue a work item using schedule_delayed_work() the
used wq is "system_wq" (per-cpu wq) while queue_delayed_work() use
WORK_CPU_UNBOUND (used when a cpu is not specified). The same applies to
schedule_work() that is using system_wq and queue_work(), that makes use
again of WORK_CPU_UNBOUND.

This lack of consistency cannot be addressed without refactoring the API.

system_unbound_wq should be the default workqueue so as not to enforce
locality constraints for random work whenever it's not required.

Adding system_dfl_wq to encourage its use when unbound work should be used.

The old system_unbound_wq will be kept for a few release cycles.

Suggested-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Marco Crivellari <marco.crivellari@suse.com>
Link: https://patch.msgid.link/20251030154739.262582-2-marco.crivellari@suse.com
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Author: DispatchCode

drivers/acpi/scan.c

@@ -2397,7 +2397,7 @@ static bool acpi_scan_clear_dep_queue(struct acpi_device *adev)
 	 * initial enumeration of devices is complete, put it into the unbound
 	 * workqueue.
 	 */
-	queue_work(system_unbound_wq, &cdw->work);
+	queue_work(system_dfl_wq, &cdw->work);
 
 	return true;
 }