x86/tboot: Convert to hotplug state machine

Install the callbacks via the state machine and let the core invoke
the callbacks on the already online CPUs.

Signed-off-by: Richard Cochran <rcochran@linutronix.de>
Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de>
Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Gang Wei <gang.wei@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Ning Sun <ning.sun@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Richard L Maliszewski <richard.l.maliszewski@intel.com>
Cc: Shane Wang <shane.wang@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: rt@linutronix.de
Cc: tboot-devel@lists.sourceforge.net
Link: http://lkml.kernel.org/r/20160713153337.400227322@linutronix.de


Signed-off-by: Ingo Molnar <mingo@kernel.org>