arm, kvm: fix double lock on cpu_add_remove_lock

Commit 8146875d (arm, kvm: Fix CPU hotplug callback registration)
holds the lock before calling the two functions:

	kvm_vgic_hyp_init()
	kvm_timer_hyp_init()

and both the two functions are calling register_cpu_notifier()
to register cpu notifier, so cause double lock on cpu_add_remove_lock.

Considered that both two functions are only called inside
kvm_arch_init() with holding cpu_add_remove_lock, so simply use
__register_cpu_notifier() to fix the problem.

Fixes: 8146875d (arm, kvm: Fix CPU hotplug callback registration)
Signed-off-by: Ming Lei <tom.leiming@gmail.com>
Reviewed-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

virt/kvm/arm/arch_timer.c

@@ -277,7 +277,7 @@ int kvm_timer_hyp_init(void)
 
 	host_vtimer_irq = ppi;
 
-	err = register_cpu_notifier(&kvm_timer_cpu_nb);
+	err = __register_cpu_notifier(&kvm_timer_cpu_nb);
 	if (err) {
 		kvm_err("Cannot register timer CPU notifier\n");
 		goto out_free;

virt/kvm/arm/vgic.c

@@ -1496,7 +1496,7 @@ int kvm_vgic_hyp_init(void)
 		goto out;
 	}
 
-	ret = register_cpu_notifier(&vgic_cpu_nb);
+	ret = __register_cpu_notifier(&vgic_cpu_nb);
 	if (ret) {
 		kvm_err("Cannot register vgic CPU notifier\n");
 		goto out_free_irq;