net/xen-netback: Remove unused code in xenvif_rx_action

The variables old_req_cons and ring_slots_used are assigned but never
used since commit 1650d5455bd2dc6b5ee134bd6fc1a3236c266b5b "xen-netback:
always fully coalesce guest Rx packets".

Signed-off-by: Julien Grall <julien.grall@citrix.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>
Cc: Ian Campbell <ian.campbell@citrix.com>
Cc: netdev@vger.kernel.org
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/xen-netback/netback.c

@@ -515,14 +515,9 @@ static void xenvif_rx_action(struct xenvif_queue *queue)
 
 	while (xenvif_rx_ring_slots_available(queue, XEN_NETBK_RX_SLOTS_MAX)
 	       && (skb = xenvif_rx_dequeue(queue)) != NULL) {
-		RING_IDX old_req_cons;
-		RING_IDX ring_slots_used;
-
 		queue->last_rx_time = jiffies;
 
-		old_req_cons = queue->rx.req_cons;
 		XENVIF_RX_CB(skb)->meta_slots_used = xenvif_gop_skb(skb, &npo, queue);
-		ring_slots_used = queue->rx.req_cons - old_req_cons;
 
 		__skb_queue_tail(&rxq, skb);
 	}