hv_netvsc: introduce netif-msg into netvsc module

1. Introduce netif-msg to netvsc to control debug logging output
and keep msg_enable in netvsc_device_context so that it is
kept persistently.
2. Only call dump_rndis_message() when NETIF_MSG_RX_ERR or above
is specified in netvsc module debug param.
In non-debug mode, in current code, dump_rndis_message() will not
dump anything but it still initialize some local variables and
process the switch logic which is unnecessary, especially in
high network throughput situation.

Signed-off-by: Simon Xiao <sixiao@microsoft.com>
Reviewed-by: K. Y. Srinivasan <kys@microsoft.com>
Reviewed-by: Haiyang Zhang <haiyangz@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/hyperv/hyperv_net.h

@@ -612,6 +612,15 @@ struct multi_send_data {
 	u32 count; /* counter of batched packets */
 };
 
+/* The context of the netvsc device  */
+struct net_device_context {
+	/* point back to our device context */
+	struct hv_device *device_ctx;
+	struct delayed_work dwork;
+	struct work_struct work;
+	u32 msg_enable; /* debug level */
+};
+
 /* Per netvsc device */
 struct netvsc_device {
 	struct hv_device *dev;
@@ -667,6 +676,9 @@ struct netvsc_device {
 	struct multi_send_data msd[NR_CPUS];
 	u32 max_pkt; /* max number of pkt in one send, e.g. 8 */
 	u32 pkt_align; /* alignment bytes, e.g. 8 */
+
+	/* The net device context */
+	struct net_device_context *nd_ctx;
 };
 
 /* NdisInitialize message */