drivers/net: const-ify ethtool_ops declarations

Signed-off-by: Jeff Garzik <jeff@garzik.org>
diff --git a/drivers/net/sis190.c b/drivers/net/sis190.c
index 7c1982a..e8f26b7 100644
--- a/drivers/net/sis190.c
+++ b/drivers/net/sis190.c
@@ -1747,7 +1747,7 @@
 	tp->msg_enable = value;
 }
 
-static struct ethtool_ops sis190_ethtool_ops = {
+static const struct ethtool_ops sis190_ethtool_ops = {
 	.get_settings	= sis190_get_settings,
 	.set_settings	= sis190_set_settings,
 	.get_drvinfo	= sis190_get_drvinfo,