drm/nouveau: Fix copy-paste error in nouveau_fence_wait_uevent_handler

Like other cases, it should use rcu protected 'chan' rather
than 'fence->channel' in nouveau_fence_wait_uevent_handler.

Fixes: 0ec5f02f ("drm/nouveau: prevent stale fence->channel pointers, and protect with rcu")
Signed-off-by: NYueHaibing <yuehaibing@huawei.com>
Signed-off-by: NBen Skeggs <bskeggs@redhat.com>

drivers/gpu/drm/nouveau/nouveau_fence.c

@@ -156,7 +156,7 @@ nouveau_fence_wait_uevent_handler(struct nvif_notify *notify)
 
 		fence = list_entry(fctx->pending.next, typeof(*fence), head);
 		chan = rcu_dereference_protected(fence->channel, lockdep_is_held(&fctx->lock));
-		if (nouveau_fence_update(fence->channel, fctx))
+		if (nouveau_fence_update(chan, fctx))
 			ret = NVIF_NOTIFY_DROP;
 	}
 	spin_unlock_irqrestore(&fctx->lock, flags);