sched/hotplug: Move migration CPU_DYING to sched_cpu_dying()

Remove the hotplug notifier and make it an explicit state.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20160310120025.502222097@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
diff --git a/kernel/cpu.c b/kernel/cpu.c
index c134a35..d6eeb8c 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -1223,7 +1223,7 @@
 	[CPUHP_AP_SCHED_STARTING] = {
 		.name			= "sched:starting",
 		.startup		= sched_cpu_starting,
-		.teardown		= NULL,
+		.teardown		= sched_cpu_dying,
 	},
 	/*
 	 * Low level startup/teardown notifiers. Run with interrupts