debug: softlockup looping fix

Rafael J. Wysocki reported weird, multi-seconds delays during
suspend/resume and bisected it back to:

  commit 82a1fcb9
  Author: Ingo Molnar <mingo@elte.hu>
  Date:   Fri Jan 25 21:08:02 2008 +0100

      softlockup: automatically detect hung TASK_UNINTERRUPTIBLE tasks

fix it:

 - restore the old wakeup mechanism
 - fix break usage in do_each_thread() { } while_each_thread().
 - fix the hotplug switch stmt, a fall-through case was broken.

Bisected-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Tested-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Acked-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>