Move x86_64 idle notifiers to generic

Move the x86_64 idle notifiers originally by Andi Kleen and Venkatesh
Pallipadi to generic.

Change-Id: Idf29cda15be151f494ff245933c12462643388d5
Acked-by: Nicolas Pitre <nicolas.pitre@linaro.org>
Signed-off-by: Todd Poynor <toddpoynor@google.com>
diff --git a/include/linux/cpu.h b/include/linux/cpu.h
index c0fb6b1..42702f2 100644
--- a/include/linux/cpu.h
+++ b/include/linux/cpu.h
@@ -291,4 +291,11 @@
 bool cpu_report_death(void);
 #endif /* #ifdef CONFIG_HOTPLUG_CPU */
 
+#define IDLE_START 1
+#define IDLE_END 2
+
+void idle_notifier_register(struct notifier_block *n);
+void idle_notifier_unregister(struct notifier_block *n);
+void idle_notifier_call_chain(unsigned long val);
+
 #endif /* _LINUX_CPU_H_ */