drivers/net: const-ify ethtool_ops declarations

Signed-off-by: Jeff Garzik <jeff@garzik.org>
diff --git a/drivers/net/r8169.c b/drivers/net/r8169.c
index ebb948b..c3015d6 100644
--- a/drivers/net/r8169.c
+++ b/drivers/net/r8169.c
@@ -1124,7 +1124,7 @@
 }
 
 
-static struct ethtool_ops rtl8169_ethtool_ops = {
+static const struct ethtool_ops rtl8169_ethtool_ops = {
 	.get_drvinfo		= rtl8169_get_drvinfo,
 	.get_regs_len		= rtl8169_get_regs_len,
 	.get_link		= ethtool_op_get_link,