leds: trigger: Replace use of system_wq() with system_percpu_wq()

Currently if a user enqueues 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.

This patch continues the effort to refactor worqueue APIs, which has begun
with the change introducing new workqueues and a new alloc_workqueue flag:

commit 128ea9f ("workqueue: Add system_percpu_wq and system_dfl_wq")
commit 930c2ea ("workqueue: Add new WQ_PERCPU flag")

system_wq should be the per-cpu workqueue, yet in this name nothing makes
that clear, so replace system_wq with system_percpu_wq.

The old wq (system_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/20251105111924.141555-1-marco.crivellari@suse.com
Signed-off-by: Lee Jones <lee@kernel.org>

Author: DispatchCode

drivers/leds/trigger/ledtrig-input-events.c

@@ -66,7 +66,7 @@ static void input_events_event(struct input_handle *handle, unsigned int type,
 
 	spin_unlock_irqrestore(&data->lock, flags);
 
-	mod_delayed_work(system_wq, &data->work, led_off_delay);
+	mod_delayed_work(system_percpu_wq, &data->work, led_off_delay);
 }
 
 static int input_events_connect(struct input_handler *handler, struct input_dev *dev,