hv_netvsc: Fix rndis_filter_close error during netvsc_remove

We now remove rndis filter before unregister_netdev(), which calls
device close. It involves closing rndis filter already removed.

This patch fixes this error.

Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>