PM / OPP: using kfree_rcu() to simplify the code

The callback function of call_rcu() just calls a kfree(), so we
can use kfree_rcu() instead of call_rcu() + callback function.

dpatch engine is used to auto generate this patch.
(https://github.com/weiyj/dpatch)

Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/base/power/opp.c

@@ -460,17 +460,6 @@ int opp_add(struct device *dev, unsigned long freq, unsigned long u_volt)
 	return 0;
 }
 
-/**
- * opp_free_rcu() - helper to clear the struct opp when grace period has
- * elapsed without blocking the the caller of opp_set_availability
- */
-static void opp_free_rcu(struct rcu_head *head)
-{
-	struct opp *opp = container_of(head, struct opp, head);
-
-	kfree(opp);
-}
-
 /**
  * opp_set_availability() - helper to set the availability of an opp
  * @dev:		device for which we do this operation
@@ -542,7 +531,7 @@ static int opp_set_availability(struct device *dev, unsigned long freq,
 
 	list_replace_rcu(&opp->node, &new_opp->node);
 	mutex_unlock(&dev_opp_list_lock);
-	call_rcu(&opp->head, opp_free_rcu);
+	kfree_rcu(opp, head);
 
 	/* Notify the change of the OPP availability */
 	if (availability_req)