virtio-net: fix mismatch of getting tx-frames

Since virtio-net allows switching napi_tx for per txq, we have to
get the specific txq's result now.

Fixes: 394bd877 ("virtio_net: support per queue interrupt coalesce command")
Cc: Gavin Li <gavinl@nvidia.com>
Signed-off-by: Heng Qi <hengqi@linux.alibaba.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/virtio_net.c

@@ -3453,7 +3453,7 @@ static int virtnet_get_per_queue_coalesce(struct net_device *dev,
 	} else {
 		ec->rx_max_coalesced_frames = 1;
 
-		if (vi->sq[0].napi.weight)
+		if (vi->sq[queue].napi.weight)
 			ec->tx_max_coalesced_frames = 1;
 	}