a patch from Henrik Austad did this:

>> Do not declare select_task_rq as part of sched_class when CONFIG_SMP is
>> not set.

Peter observed:

> While a proper cleanup, could you do it by re-arranging the methods so
> as to not create an additional ifdef?

Do not declare select_task_rq and some other methods as part of sched_class
when CONFIG_SMP is not set.

Also gather those methods to avoid CONFIG_SMP mess.
Idea-by: NHenrik Austad <henrik.austad@gmail.com>
Signed-off-by: NLi Zefan <lizf@cn.fujitsu.com>
Acked-by: NPeter Zijlstra <peterz@infradead.org>
Acked-by: NHenrik Austad <henrik@austad.us>
Signed-off-by: NIngo Molnar <mingo@elte.hu>