drivers/net: const-ify ethtool_ops declarations

Signed-off-by: Jeff Garzik <jeff@garzik.org>
diff --git a/drivers/net/rionet.c b/drivers/net/rionet.c
index 12cde06..b7ff484 100644
--- a/drivers/net/rionet.c
+++ b/drivers/net/rionet.c
@@ -427,7 +427,7 @@
 	rnet->msg_enable = value;
 }
 
-static struct ethtool_ops rionet_ethtool_ops = {
+static const struct ethtool_ops rionet_ethtool_ops = {
 	.get_drvinfo = rionet_get_drvinfo,
 	.get_msglevel = rionet_get_msglevel,
 	.set_msglevel = rionet_set_msglevel,