workqueue: Simplify a pr_warn() call in wq_select_unbound_cpu()

Use pr_warn_once() to achieve the same thing. It's simpler.
Signed-off-by: Ammar Faizi <ammarfaizi2@gnuweeb.org>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

kernel/workqueue.c

@@ -1392,15 +1392,13 @@ static bool is_chained_work(struct workqueue_struct *wq)
  */
 static int wq_select_unbound_cpu(int cpu)
 {
-	static bool printed_dbg_warning;
 	int new_cpu;
 
 	if (likely(!wq_debug_force_rr_cpu)) {
 		if (cpumask_test_cpu(cpu, wq_unbound_cpumask))
 			return cpu;
-	} else if (!printed_dbg_warning) {
-		pr_warn("workqueue: round-robin CPU selection forced, expect performance impact\n");
-		printed_dbg_warning = true;
+	} else {
+		pr_warn_once("workqueue: round-robin CPU selection forced, expect performance impact\n");
 	}
 
 	if (cpumask_empty(wq_unbound_cpumask))