drivers/net: const-ify ethtool_ops declarations

Signed-off-by: Jeff Garzik <jeff@garzik.org>
diff --git a/drivers/net/sunbmac.c b/drivers/net/sunbmac.c
index d468915..9e4be86 100644
--- a/drivers/net/sunbmac.c
+++ b/drivers/net/sunbmac.c
@@ -1071,7 +1071,7 @@
 	return (bp->sw_bmsr & BMSR_LSTATUS);
 }
 
-static struct ethtool_ops bigmac_ethtool_ops = {
+static const struct ethtool_ops bigmac_ethtool_ops = {
 	.get_drvinfo		= bigmac_get_drvinfo,
 	.get_link		= bigmac_get_link,
 };