tick: broadcast: Prevent livelock from event handler

With the removal of the hrtimer softirq the switch to highres/nohz
mode happens in the tick interrupt. That leads to a livelock when the
per cpu event handler is directly called from the broadcast handler
under broadcast lock because broadcast lock needs to be taken for the
highres/nohz switch as well.

Solve this by calling the cpu local handler outside the broadcast_lock
held region.

Fixes: c6eb3f70 "hrtimer: Get rid of hrtimer softirq"
Reported-and-tested-by: Borislav Petkov <bp@alien8.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>