sched/rt: Make init_sched_rt_calss() __init

It's a bootstrap function.

Signed-off-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/52F5CC09.1080502@huawei.com


Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>