stop_machine: Use smpboot threads

Use the smpboot thread infrastructure. Mark the stopper
thread
selfparking and park it after it has finished the
take_cpu_down()
work.

Signed-off-by: Thomas Gleixner
<tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rusty
Russell <rusty@rustcorp.com.au>
Cc: Paul McKenney
<paulmck@linux.vnet.ibm.com>
Cc: Srivatsa S. Bhat
<srivatsa.bhat@linux.vnet.ibm.com>
Cc: Arjan van de Veen
<arjan@infradead.org>
Cc: Paul Turner <pjt@google.com>
Cc: Richard
Weinberger <rw@linutronix.de>
Cc: Magnus Damm
<magnus.damm@gmail.com>
Link:
http://lkml.kernel.org/r/20130131120741.686315164@linutronix.de
Signed-off-by:
Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: franciscofranco
<franciscofranco.1990@gmail.com>

idea is taken here -
https://github.com/franciscofranco/M8/commit/3117ae80dc4a314a54397bac045f9dd659dae4f6