ARM/shmobile: Convert to hotplug state machine

Install the callbacks via the state machine so the old notifier based
cpuhotplug infrastructure can be removed.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: linux-sh@vger.kernel.org
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Magnus Damm <magnus.damm@gmail.com>
Cc: Simon Horman <horms@verge.net.au>
Cc: rt@linutronix.de
Cc: linux-arm-kernel@lists.infradead.org
Link: http://lkml.kernel.org/r/20160906170457.32393-3-bigeasy@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>