drivers/net: const-ify ethtool_ops declarations

Signed-off-by: Jeff Garzik <jeff@garzik.org>
diff --git a/drivers/net/3c501.c b/drivers/net/3c501.c
index 591e7fb..1b82bcc 100644
--- a/drivers/net/3c501.c
+++ b/drivers/net/3c501.c
@@ -881,7 +881,7 @@
 	debug = level;
 }
 
-static struct ethtool_ops netdev_ethtool_ops = {
+static const struct ethtool_ops netdev_ethtool_ops = {
 	.get_drvinfo		= netdev_get_drvinfo,
 	.get_msglevel		= netdev_get_msglevel,
 	.set_msglevel		= netdev_set_msglevel,