usbnet: make ethtool_ops const

The ethtool_ops table of function pointers should be const.
Fix all the usb network drivers.

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/usb/cdc_ncm.c b/drivers/net/usb/cdc_ncm.c
index 009dd0f..47fca6f 100644
--- a/drivers/net/usb/cdc_ncm.c
+++ b/drivers/net/usb/cdc_ncm.c
@@ -138,7 +138,7 @@
 static void cdc_ncm_tx_timeout(unsigned long arg);
 static const struct driver_info cdc_ncm_info;
 static struct usb_driver cdc_ncm_driver;
-static struct ethtool_ops cdc_ncm_ethtool_ops;
+static const struct ethtool_ops cdc_ncm_ethtool_ops;
 
 static const struct usb_device_id cdc_devs[] = {
 	{ USB_INTERFACE_INFO(USB_CLASS_COMM,
@@ -1220,7 +1220,7 @@
 	.supports_autosuspend = 1,
 };
 
-static struct ethtool_ops cdc_ncm_ethtool_ops = {
+static const struct ethtool_ops cdc_ncm_ethtool_ops = {
 	.get_drvinfo = cdc_ncm_get_drvinfo,
 	.get_link = usbnet_get_link,
 	.get_msglevel = usbnet_get_msglevel,