sched: add sanity check in partition_sched_domains()

Impact: cleanup, add debug check

It's wrong to make dattr_new = NULL if doms_new == NULL, it introduces
memory leak if dattr_new != NULL. Fortunately dattr_new is always NULL
in this case. So remove the code and add a sanity check.

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

kernel/sched.c

@@ -7767,7 +7767,7 @@ match1:
 		ndoms_cur = 0;
 		doms_new = &fallback_doms;
 		cpus_andnot(doms_new[0], cpu_online_map, cpu_isolated_map);
-		dattr_new = NULL;
+		WARN_ON_ONCE(dattr_new);
 	}
 
 	/* Build new domains */