P-RES: fix rare deadlock via hrtimer_start()

There's a rare condition under which the current call to hrtimer_start()
in pres_update_timer() may result in deadlock.

pres_update_timer() // holds runqueue lock and state->lock
-> hrtimer_start()
  -> raise_softirq_irqoff()
    -> wakeup_softirqd()
      ->  wake_up_process()
        -> acquires runqueue lock()

To avoid this, we need to call __hrtimer_start_range_ns() with the
'wakeup' flag set to zero.

While at it, also drop the state->lock before calling into hrtimer(),
to avoid making the scheduler critical section longer than necessary.