drivers/net: const-ify ethtool_ops declarations

Signed-off-by: Jeff Garzik <jeff@garzik.org>
diff --git a/drivers/net/ixgb/ixgb_ethtool.c b/drivers/net/ixgb/ixgb_ethtool.c
index ba62108..64a383e 100644
--- a/drivers/net/ixgb/ixgb_ethtool.c
+++ b/drivers/net/ixgb/ixgb_ethtool.c
@@ -699,7 +699,7 @@
 	}
 }
 
-static struct ethtool_ops ixgb_ethtool_ops = {
+static const struct ethtool_ops ixgb_ethtool_ops = {
 	.get_settings = ixgb_get_settings,
 	.set_settings = ixgb_set_settings,
 	.get_drvinfo = ixgb_get_drvinfo,