cpuidle driver initializes the cpuidle_device structure for each CPU device
and registers with cpuidle using cpuidle_register_device.
+If all the idle states are the same, the wrapper function cpuidle_register
+could be used instead.
+
It can also support the dynamic changes (like battery <-> AC), by using
cpuidle_pause_and_lock, cpuidle_disable_device and cpuidle_enable_device,
cpuidle_resume_and_unlock.
Interfaces:
+extern int cpuidle_register(struct cpuidle_driver *drv,
+ const struct cpumask *const coupled_cpus);
+extern int cpuidle_unregister(struct cpuidle_driver *drv);
extern int cpuidle_register_driver(struct cpuidle_driver *drv);
extern void cpuidle_unregister_driver(struct cpuidle_driver *drv);
extern int cpuidle_register_device(struct cpuidle_device *dev);