drivers/net: const-ify ethtool_ops declarations

Signed-off-by: Jeff Garzik <jeff@garzik.org>
diff --git a/drivers/net/pcnet32.c b/drivers/net/pcnet32.c
index de05aeb..21dc68e 100644
--- a/drivers/net/pcnet32.c
+++ b/drivers/net/pcnet32.c
@@ -1499,7 +1499,7 @@
 	spin_unlock_irqrestore(&lp->lock, flags);
 }
 
-static struct ethtool_ops pcnet32_ethtool_ops = {
+static const struct ethtool_ops pcnet32_ethtool_ops = {
 	.get_settings		= pcnet32_get_settings,
 	.set_settings		= pcnet32_set_settings,
 	.get_drvinfo		= pcnet32_get_drvinfo,