drivers/net: const-ify ethtool_ops declarations

Signed-off-by: Jeff Garzik <jeff@garzik.org>
diff --git a/drivers/net/spider_net.h b/drivers/net/spider_net.h
index 30407cd..2e80882 100644
--- a/drivers/net/spider_net.h
+++ b/drivers/net/spider_net.h
@@ -29,7 +29,7 @@
 extern int spider_net_stop(struct net_device *netdev);
 extern int spider_net_open(struct net_device *netdev);
 
-extern struct ethtool_ops spider_net_ethtool_ops;
+extern const struct ethtool_ops spider_net_ethtool_ops;
 
 extern char spider_net_driver_name[];