hyperv: Add netpoll support

In order to have at least a netconsole to debug kernel issues on
Windows Azure this patch implements netpoll support.
Sending packets is easy, netvsc_start_xmit() does already everything
needed.
Signed-off-by: NRichard Weinberger <richard@nod.at>
Acked-by: NHaiyang Zhang <haiyangz@microsoft.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/hyperv/netvsc_drv.c

@@ -749,6 +749,14 @@ static int netvsc_set_mac_addr(struct net_device *ndev, void *p)
 	return err;
 }
 
+#ifdef CONFIG_NET_POLL_CONTROLLER
+static void netvsc_poll_controller(struct net_device *net)
+{
+	/* As netvsc_start_xmit() works synchronous we don't have to
+	 * trigger anything here.
+	 */
+}
+#endif
 
 static const struct ethtool_ops ethtool_ops = {
 	.get_drvinfo	= netvsc_get_drvinfo,
@@ -764,6 +772,9 @@ static const struct net_device_ops device_ops = {
 	.ndo_validate_addr =		eth_validate_addr,
 	.ndo_set_mac_address =		netvsc_set_mac_addr,
 	.ndo_select_queue =		netvsc_select_queue,
+#ifdef CONFIG_NET_POLL_CONTROLLER
+	.ndo_poll_controller =		netvsc_poll_controller,
+#endif
 };
 
 /*