virtio: simplify the using of received in virtnet_poll

received is 0, no need to minus it and use "+=" to reassign it

Signed-off-by: Li RongQing <roy.qing.li@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 4e84236..a829930 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -749,9 +749,9 @@
 {
 	struct receive_queue *rq =
 		container_of(napi, struct receive_queue, napi);
-	unsigned int r, received = 0;
+	unsigned int r, received;
 
-	received += virtnet_receive(rq, budget - received);
+	received = virtnet_receive(rq, budget);
 
 	/* Out of packets? */
 	if (received < budget) {