PM / Domains: Add a detach callback to the struct dev_pm_domain

The intent of this callback is to simplify detachment of devices from
their PM domains. Further patches will show the benefit.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Reviewed-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

include/linux/pm.h

@@ -619,6 +619,7 @@ extern int dev_pm_put_subsys_data(struct device *dev);
  */
 struct dev_pm_domain {
 	struct dev_pm_ops	ops;
+	void (*detach)(struct device *dev, bool power_off);
 };
 
 /*