Revert "arm64, debug-monitors: Fix CPU hotplug callback registration"

This reverts commit b057e1d80f916922081c7c5bd2c08ff53ed9e4fc.
diff --git a/arch/arm64/kernel/debug-monitors.c b/arch/arm64/kernel/debug-monitors.c
index d202656..eafcaed 100644
--- a/arch/arm64/kernel/debug-monitors.c
+++ b/arch/arm64/kernel/debug-monitors.c
@@ -157,16 +157,12 @@
 
 static int __cpuinit debug_monitors_init(void)
 {
-	cpu_notifier_register_begin();
-
 	/* Clear the OS lock. */
 	smp_call_function(clear_os_lock, NULL, 1);
 	clear_os_lock(NULL);
 
 	/* Register hotplug handler. */
-	__register_cpu_notifier(&os_lock_nb);
-
-	cpu_notifier_register_done();
+	register_cpu_notifier(&os_lock_nb);
 	return 0;
 }
 postcore_initcall(debug_monitors_init);