sched/rt, workqueue: Use PREEMPTION

CONFIG_PREEMPTION is selected by CONFIG_PREEMPT and by CONFIG_PREEMPT_RT.
Both PREEMPT and PREEMPT_RT require the same functionality which today
depends on CONFIG_PREEMPT.

Update the comment to use PREEMPTION because it is true for both
preemption models.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20191015191821.11479-35-bigeasy@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>

kernel/workqueue.c

@@ -2280,7 +2280,7 @@ __acquires(&pool->lock)
 	}
 
 	/*
-	 * The following prevents a kworker from hogging CPU on !PREEMPT
+	 * The following prevents a kworker from hogging CPU on !PREEMPTION
 	 * kernels, where a requeueing work item waiting for something to
 	 * happen could deadlock with stop_machine as such work item could
 	 * indefinitely requeue itself while all other CPUs are trapped in