clocksource: Rework stale comment

AFAICS the hotplug code no longer uses this function.

Signed-off-by: Peter Zijlstra (Intel) <[e-mail]>
Signed-off-by: Thomas Gleixner <[e-mail]>
Reviewed-by: Rafael J. Wysocki <[e-mail]>
Cc: [e-mail]
Cc: [e-mail]
Cc: [e-mail]
Cc: [e-mail]
Link: https://lkml.kernel.org/r/[e-mail]

kernel/time/clocksource.c

···
  * clocksource_mark_unstable - mark clocksource unstable via watchdog
  * @cs:		clocksource to be marked unstable
  *
- * This function is called instead of clocksource_change_rating from
- * cpu hotplug code to avoid a deadlock between the clocksource mutex
- * and the cpu hotplug mutex. It defers the update of the clocksource
- * to the watchdog thread.
+ * This function is called by the x86 TSC code to mark clocksources as unstable;
+ * it defers demotion and re-selection to a kthread.
  */
 void clocksource_mark_unstable(struct clocksource *cs)
 {