fault-injection/cpu: Convert to hotplug state machine

Install the callbacks via the state machine.

This is just a temporary vehicle to keep the interface working for now,
It'll be replaced by the sysfs interface which allows to step through the
hotplug state machine step by step.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Akinobu Mita <akinobu.mita@gmail.com>
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20160906170457.32393-15-bigeasy@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>