mutex: Move mutex spinning code from sched/core.c back to mutex.c

Signed-off-by: Waiman Long<Waiman.Long@hp.com>
Signed-off-by: Francisco Franco <franciscofranco.1990@gmail.com>
Signed-off-by: nicholas <firepoison35@gmail.com>

Conflicts:
	include/linux/sched.h
	kernel/sched/features.h