Moved scheduler from containers back to being a global.

It makes more sense to have a scheduler (or runqueue pair) per-cpu
rather than per-container. This provides more flexible global scheduling
policy that is also simpler due to all scheduling details being controlled
from a single point.

include/l4/generic/scheduler.h

@@ -55,6 +55,7 @@ struct scheduler {
 	/* Total priority of all tasks in container */
 	int prio_total;
 };
+extern struct scheduler scheduler;
 
 void sched_init_runqueue(struct runqueue *rq);
 void sched_init_task(struct ktcb *task, int priority);