hv_netvsc: change GPAD teardown order on older versions

On older versions of Windows, the host ignores messages after
vmbus channel is closed.

Workaround this by doing what Windows does and send the teardown
before close on older versions of NVSP protocol.
Reported-by: Mohammed Gamal <mgamal@redhat.com>
Fixes: 0cf73780 ("hv_netvsc: netvsc_teardown_gpadl() split")
Signed-off-by: Stephen Hemminger <sthemmin@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/hyperv/netvsc.c

@@ -571,9 +571,14 @@ void netvsc_device_remove(struct hv_device *device)
 	 */
 	netdev_dbg(ndev, "net device safe to remove\n");
 
+	/* older versions require that buffer be revoked before close */
+	if (net_device->nvsp_version < NVSP_PROTOCOL_VERSION_4)
+		netvsc_teardown_gpadl(device, net_device);
+
 	/* Now, we can close the channel safely */
 	vmbus_close(device->channel);
 
+	if (net_device->nvsp_version >= NVSP_PROTOCOL_VERSION_4)
 		netvsc_teardown_gpadl(device, net_device);
 
 	/* Release all resources */