virtio-net: remove unused skb_vnet_hdr->num_sg field

[Split from "correct capacity math on ring full" -- Rusty]
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Acked-by: Michael S. Tsirkin <mst@redhat.com>

drivers/net/virtio_net.c

@@ -95,7 +95,6 @@ struct skb_vnet_hdr {
 		struct virtio_net_hdr hdr;
 		struct virtio_net_hdr_mrg_rxbuf mhdr;
 	};
-	unsigned int num_sg;
 };
 
 struct padded_vnet_hdr {
@@ -579,6 +578,7 @@ static int xmit_skb(struct virtnet_info *vi, struct sk_buff *skb)
 {
 	struct skb_vnet_hdr *hdr = skb_vnet_hdr(skb);
 	const unsigned char *dest = ((struct ethhdr *)skb->data)->h_dest;
+	unsigned num_sg;
 
 	pr_debug("%s: xmit %p %pM\n", vi->dev->name, skb, dest);
 
@@ -617,8 +617,8 @@ static int xmit_skb(struct virtnet_info *vi, struct sk_buff *skb)
 	else
 		sg_set_buf(vi->tx_sg, &hdr->hdr, sizeof hdr->hdr);
 
-	hdr->num_sg = skb_to_sgvec(skb, vi->tx_sg + 1, 0, skb->len) + 1;
-	return virtqueue_add_buf(vi->svq, vi->tx_sg, hdr->num_sg,
+	num_sg = skb_to_sgvec(skb, vi->tx_sg + 1, 0, skb->len) + 1;
+	return virtqueue_add_buf(vi->svq, vi->tx_sg, num_sg,
 				 0, skb, GFP_ATOMIC);
 }