hrtimer: Remove the comment about not used HRTIMER_SOFTIRQ

The softirq `HRTIMER_SOFTIRQ' was not used since commit c6eb3f70d448
("hrtimer: Get rid of hrtimer softirq").

But it got used again, beginning with commit 5da70160462e ("hrtimer:
Implement support for softirq based hrtimers"), which did not remove the
comment. Remove it now.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20191107091924.13410-1-bigeasy@linutronix.de

diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
index 89fc59d..963c3c6 100644
--- a/include/linux/interrupt.h
+++ b/include/linux/interrupt.h
@@ -520,8 +520,7 @@ enum
 	IRQ_POLL_SOFTIRQ,
 	TASKLET_SOFTIRQ,
 	SCHED_SOFTIRQ,
-	HRTIMER_SOFTIRQ, /* Unused, but kept as tools rely on the
-			    numbering. Sigh! */
+	HRTIMER_SOFTIRQ,
 	RCU_SOFTIRQ,    /* Preferable RCU should always be the last softirq */
 
 	NR_SOFTIRQS