drivers/net: const-ify ethtool_ops declarations

Signed-off-by: Jeff Garzik <jeff@garzik.org>

drivers/net/e1000/e1000_ethtool.c

@@ -1922,7 +1922,7 @@ e1000_get_strings(struct net_device *netdev, uint32_t stringset, uint8_t *data)
 	}
 }
 
-static struct ethtool_ops e1000_ethtool_ops = {
+static const struct ethtool_ops e1000_ethtool_ops = {
 	.get_settings           = e1000_get_settings,
 	.set_settings           = e1000_set_settings,
 	.get_drvinfo            = e1000_get_drvinfo,