drivers/net: const-ify ethtool_ops declarations

Signed-off-by: Jeff Garzik <jeff@garzik.org>
diff --git a/drivers/net/3c501.h b/drivers/net/3c501.h
index 965474a..39d3324 100644
--- a/drivers/net/3c501.h
+++ b/drivers/net/3c501.h
@@ -13,7 +13,7 @@
 static int  el1_close(struct net_device *dev);
 static struct net_device_stats *el1_get_stats(struct net_device *dev);
 static void set_multicast_list(struct net_device *dev);
-static struct ethtool_ops netdev_ethtool_ops;
+static const struct ethtool_ops netdev_ethtool_ops;
 
 #define EL1_IO_EXTENT	16