sched: Use replace normalize_task() with __sched_setscheduler()

sched: Use replace normalize_task() with __sched_setscheduler()

Reduce duplicate logic; normalize_task() is a simplified version of
__sched_setscheduler(). Parametrize the difference and collapse.

This reduces the amount of check_class_changed() sites.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: ktkhai@parallels.com
Cc: rostedt@goodmis.org
Cc: juri.lelli@gmail.com
Cc: pang.xunlei@linaro.org
Cc: oleg@redhat.com
Cc: wanpeng.li@linux.intel.com
Cc: umgwanakikbuti@gmail.com
Link: http://lkml.kernel.org/r/20150611124742.532642391@infradead.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>