RAS/CEC: Replace use of system_wq with system_percpu_wq

Switch to using system_percpu_wq because system_wq is going away as part of
a workqueue restructuring.

Currently if a user enqueues a work item using schedule_delayed_work() the
used workqueue is "system_wq" (per-cpu workqueue) while queue_delayed_work()
uses 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 of
WORK_CPU_UNBOUND again.

This lack of consistency cannot be addressed without refactoring the API.
For more details see those commits and the Link tag below.

128ea9f6ccfb ("workqueue: Add system_percpu_wq and system_dfl_wq")
930c2ea566af ("workqueue: Add new WQ_PERCPU flag")

[ bp: Massage commit message. ]

Suggested-by: Tejun Heo <[e-mail]>
Signed-off-by: Marco Crivellari <[e-mail]>
Signed-off-by: Borislav Petkov (AMD) <[e-mail]>
Link: https://lore.kernel.org/all/[e-mail]

drivers/ras/cec.c

···
 	unsigned long iv;
 
 	iv = interval * HZ;
-	mod_delayed_work(system_wq, &cec_work, round_jiffies(iv));
+	mod_delayed_work(system_percpu_wq, &cec_work, round_jiffies(iv));
 }
 
 static void cec_work_fn(struct work_struct *work)