netvsc: call netif_receive_skb

To improve performance, netvsc can call network stack directly and
avoid the local backlog queue. This is safe since incoming packets are
handled in softirq context already because the receive function
callback is called from a tasklet.

Signed-off-by: Stephen Hemminger <sthemmin@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>