drivers/net: const-ify ethtool_ops declarations

Signed-off-by: Jeff Garzik <jeff@garzik.org>
diff --git a/drivers/net/s2io.c b/drivers/net/s2io.c
index b93751c..5420591 100644
--- a/drivers/net/s2io.c
+++ b/drivers/net/s2io.c
@@ -5736,7 +5736,7 @@
 	return 0;
 }
 
-static struct ethtool_ops netdev_ethtool_ops = {
+static const struct ethtool_ops netdev_ethtool_ops = {
 	.get_settings = s2io_ethtool_gset,
 	.set_settings = s2io_ethtool_sset,
 	.get_drvinfo = s2io_ethtool_gdrvinfo,