hv_netvsc: avoid repeated updates of packet filter

The netvsc driver can get repeated calls to netvsc_rx_mode during
network setup; each of these calls ends up scheduling the lower
layers to update tha packet filter. This update requires an
request/response to the host. So avoid doing this if we already
know that the correct packet filter value is set.

Signed-off-by: Stephen Hemminger <sthemmin@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/hyperv/hyperv_net.h b/drivers/net/hyperv/hyperv_net.h
index 0db3bd1..cd538d5 100644
--- a/drivers/net/hyperv/hyperv_net.h
+++ b/drivers/net/hyperv/hyperv_net.h
@@ -173,6 +173,7 @@ struct rndis_device {
 	struct list_head req_list;
 
 	struct work_struct mcast_work;
+	u32 filter;
 
 	bool link_state;        /* 0 - link up, 1 - link down */