clockintr: add clockqueue_reset_intrclock()

clockintr: add clockqueue_reset_intrclock()

If a call to clockintr_advance(), clockintr_cancel(), or
clockintr_schedule() changes which clockintr on a given queue is
expiring soonest, we need to rearm the queue's intrclock according
to that most imminent expiration.

Add clockqueue_reset_intrclock() and use it during the aforementioned
scheduling operations if the caller is running on the queue's
controlling CPU.

Scheduling operations are not currently run while CQ_INTRCLOCK is set,
so this patch changes no behavior yet.

clockqueue_reset_intrclock() is only part of the story.  At some point
we will also need to add IPIs to every architecture to handle the case
when the caller is not running on a queue's controlling CPU.