sched/numa: Fix is_core_idle()

Use the loop variable instead of the function argument to test the
other SMT siblings for idle.

Fixes: ff7db0b ("sched/numa: Prefer using an idle CPU as a migration target instead of comparing tasks")
Signed-off-by: Mika Penttilä <mika.penttila@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Pankaj Gupta <pankaj.gupta@ionos.com>
Link: https://lkml.kernel.org/r/20210722063946.28951-1-mika.penttila@gmail.com

kernel/sched/fair.c

@@ -1486,7 +1486,7 @@ static inline bool is_core_idle(int cpu)
 		if (cpu == sibling)
 			continue;
 
-		if (!idle_cpu(cpu))
+		if (!idle_cpu(sibling))
 			return false;
 	}
 #endif