smp/hotplug: Move step CPUHP_AP_SMPCFD_DYING to the correct place

Commit 31487f83 ("smp/cfd: Convert core to hotplug state machine")
accidently put this step on the wrong place. The step should be at the
cpuhp_ap_states[] rather than the cpuhp_bp_states[].

grep smpcfd /sys/devices/system/cpu/hotplug/states
 40: smpcfd:prepare
129: smpcfd:dying

"smpcfd:dying" was missing before.
So was the invocation of the function smpcfd_dying_cpu().

Fixes: 31487f83 ("smp/cfd: Convert core to hotplug state machine")
Signed-off-by: Lai Jiangshan <jiangshanlai@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Richard Weinberger <richard@nod.at>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: stable@vger.kernel.org
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Link: https://lkml.kernel.org/r/20171128131954.81229-1-jiangshanlai@gmail.com

kernel/cpu.c

@@ -1289,11 +1289,6 @@ static struct cpuhp_step cpuhp_bp_states[] = {
 		.teardown.single	= NULL,
 		.cant_stop		= true,
 	},
-	[CPUHP_AP_SMPCFD_DYING] = {
-		.name			= "smpcfd:dying",
-		.startup.single		= NULL,
-		.teardown.single	= smpcfd_dying_cpu,
-	},
 	/*
 	 * Handled on controll processor until the plugged processor manages
 	 * this itself.
@@ -1335,6 +1330,11 @@ static struct cpuhp_step cpuhp_ap_states[] = {
 		.startup.single		= NULL,
 		.teardown.single	= rcutree_dying_cpu,
 	},
+	[CPUHP_AP_SMPCFD_DYING] = {
+		.name			= "smpcfd:dying",
+		.startup.single		= NULL,
+		.teardown.single	= smpcfd_dying_cpu,
+	},
 	/* Entry state on starting. Interrupts enabled from here on. Transient
 	 * state for synchronsization */
 	[CPUHP_AP_ONLINE] = {