locking/rtmutex: Fix misleading comment in rt_mutex_postunlock()

Preemption is disabled in mark_wakeup_next_waiter(,) not in
rt_mutex_slowunlock().
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210326153944.341734608@linutronix.de

kernel/locking/rtmutex.c

@@ -1305,7 +1305,7 @@ void __sched rt_mutex_postunlock(struct wake_q_head *wake_q)
 {
 	wake_up_q(wake_q);
 
-	/* Pairs with preempt_disable() in rt_mutex_slowunlock() */
+	/* Pairs with preempt_disable() in mark_wakeup_next_waiter() */
 	preempt_enable();
 }