sched: fix sign check error in place_entity()

fix sign check error in place_entity() - we'd get excessive
latencies due to negatives being converted to large u64's.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>

kernel/sched_fair.c

@@ -483,7 +483,7 @@ place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
 		if (sched_feat(NEW_FAIR_SLEEPERS))
 			vruntime -= sysctl_sched_latency;
 
-		vruntime = max(vruntime, se->vruntime);
+		vruntime = max_t(s64, vruntime, se->vruntime);
 	}
 
 	se->vruntime = vruntime;