sched: RT-balance, add new methods to sched_class

Dmitry Adamushko found that the current implementation of the RT
balancing code left out changes to the sched_setscheduler and
rt_mutex_setprio.

This patch addresses this issue by adding methods to the schedule classes
to handle being switched out of (switched_from) and being switched into
(switched_to) a sched_class. Also a method for changing of priorities
is also added (prio_changed).

This patch also removes some duplicate logic between rt_mutex_setprio and
sched_setscheduler.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/include/linux/sched.h b/include/linux/sched.h
index c67d2c2..f2044e7 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -855,6 +855,13 @@
 
 	void (*join_domain)(struct rq *rq);
 	void (*leave_domain)(struct rq *rq);
+
+	void (*switched_from) (struct rq *this_rq, struct task_struct *task,
+			       int running);
+	void (*switched_to) (struct rq *this_rq, struct task_struct *task,
+			     int running);
+	void (*prio_changed) (struct rq *this_rq, struct task_struct *task,
+			     int oldprio, int running);
 };
 
 struct load_weight {