staging: hv: fix counting of available buffer slots when send fails

Because the number of available buffer slots doesn't decrease for failed
sends, we should not call netvsc_xmit_completion(), which increase the
count of available slots. In this failed case, just free the memory is
enough.

Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/staging/hv/netvsc_drv.c

@@ -190,7 +190,8 @@ static int netvsc_start_xmit(struct sk_buff *skb, struct net_device *net)
 	} else {
 		/* we are shutting down or bus overloaded, just drop packet */
 		net->stats.tx_dropped++;
-		netvsc_xmit_completion(packet);
+		kfree(packet);
+		dev_kfree_skb_any(skb);
 	}
 
 	return NETDEV_TX_OK;