hrtimer: Remove the comment about not used HRTIMER_SOFTIRQ

The softirq `HRTIMER_SOFTIRQ' was not used since commit c6eb3f7
("hrtimer: Get rid of hrtimer softirq").

But it got used again, beginning with commit 5da7016 ("hrtimer:
Implement support for softirq based hrtimers"), which did not remove the
comment. Remove it now.

Signed-off-by: Sebastian Andrzej Siewior <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]

Author: Sebastian Andrzej Siewior

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