platform: surface: replace use of system_wq with system_percpu_wq

This patch continues the effort to refactor workqueue APIs, which has begun
with the changes 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")

The point of the refactoring is to eventually alter the default behavior of
workqueues to become unbound by default so that their workload placement is
optimized by the scheduler.

Before that to happen after a careful review and conversion of each individual
case, workqueue users must be converted to the better named new workqueues with
no intended behaviour changes:

   system_wq -> system_percpu_wq
   system_unbound_wq -> system_dfl_wq

This way the old obsolete workqueues (system_wq, system_unbound_wq) can be
removed in the future.

Suggested-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Marco Crivellari <marco.crivellari@suse.com>
Link: https://lore.kernel.org/all/20250221112003.1dSuoGyc@linutronix.de/
Link: https://patch.msgid.link/20251127144125.233728-4-marco.crivellari@suse.com
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>

Author: DispatchCode

drivers/platform/surface/aggregator/ssh_packet_layer.c

@@ -671,7 +671,7 @@ static void ssh_ptl_timeout_reaper_mod(struct ssh_ptl *ptl, ktime_t now,
 	/* Re-adjust / schedule reaper only if it is above resolution delta. */
 	if (ktime_before(aexp, ptl->rtx_timeout.expires)) {
 		ptl->rtx_timeout.expires = expires;
-		mod_delayed_work(system_wq, &ptl->rtx_timeout.reaper, delta);
+		mod_delayed_work(system_percpu_wq, &ptl->rtx_timeout.reaper, delta);
 	}
 
 	spin_unlock(&ptl->rtx_timeout.lock);

drivers/platform/surface/aggregator/ssh_request_layer.c

@@ -434,7 +434,7 @@ static void ssh_rtl_timeout_reaper_mod(struct ssh_rtl *rtl, ktime_t now,
 	/* Re-adjust / schedule reaper only if it is above resolution delta. */
 	if (ktime_before(aexp, rtl->rtx_timeout.expires)) {
 		rtl->rtx_timeout.expires = expires;
-		mod_delayed_work(system_wq, &rtl->rtx_timeout.reaper, delta);
+		mod_delayed_work(system_percpu_wq, &rtl->rtx_timeout.reaper, delta);
 	}
 
 	spin_unlock(&rtl->rtx_timeout.lock);