drivers/net: const-ify ethtool_ops declarations

Signed-off-by: Jeff Garzik <jeff@garzik.org>
diff --git a/drivers/net/smc91x.c b/drivers/net/smc91x.c
index 4edfa7f..d7e5643 100644
--- a/drivers/net/smc91x.c
+++ b/drivers/net/smc91x.c
@@ -1739,7 +1739,7 @@
 	lp->msg_enable = level;
 }
 
-static struct ethtool_ops smc_ethtool_ops = {
+static const struct ethtool_ops smc_ethtool_ops = {
 	.get_settings	= smc_ethtool_getsettings,
 	.set_settings	= smc_ethtool_setsettings,
 	.get_drvinfo	= smc_ethtool_getdrvinfo,