cpu/hotplug: Let upcoming cpu bring itself fully up

cpu/hotplug: Let upcoming cpu bring itself fully up

Let the upcoming cpu kick the hotplug thread and let itself complete the
bringup. That way the controll side can just wait for the completion or later
when we made the hotplug machinery async not care at all.

Signed-off-by: Thomas Gleixner <[email protected]>
Cc: [email protected]
Cc: Rik van Riel <[email protected]>
Cc: Rafael Wysocki <[email protected]>
Cc: "Srivatsa S. Bhat" <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Arjan van de Ven <[email protected]>
Cc: Sebastian Siewior <[email protected]>
Cc: Rusty Russell <[email protected]>
Cc: Steven Rostedt <[email protected]>
Cc: Oleg Nesterov <[email protected]>
Cc: Tejun Heo <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Paul McKenney <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Paul Turner <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Thomas Gleixner <[email protected]>