net: sched: fix misuse of qcpu->backlog in gnet_stats_add_queue_cpu

In the gnet_stats_add_queue_cpu function, the qstats->qlen statistics
are incorrectly set to qcpu->backlog.

Fixes: 448e163f8b9b ("gen_stats: Add gnet_stats_add_queue()")
Signed-off-by: Zhengchao Shao <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

net/core/gen_stats.c

···
 	for_each_possible_cpu(i) {
 		const struct gnet_stats_queue *qcpu = per_cpu_ptr(q, i);
 
-		qstats->qlen += qcpu->backlog;
+		qstats->qlen += qcpu->qlen;
 		qstats->backlog += qcpu->backlog;
 		qstats->drops += qcpu->drops;
 		qstats->requeues += qcpu->requeues;