xen-netback: make ops structs const

All tables of function pointers should be const to make hacks
more difficult. Compile tested only.

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/xen-netback/interface.c b/drivers/net/xen-netback/interface.c
index 0b5c18f..b7d41f8 100644
--- a/drivers/net/xen-netback/interface.c
+++ b/drivers/net/xen-netback/interface.c
@@ -223,7 +223,7 @@
 	}
 }
 
-static struct ethtool_ops xenvif_ethtool_ops = {
+static const struct ethtool_ops xenvif_ethtool_ops = {
 	.get_link	= ethtool_op_get_link,
 
 	.get_sset_count = xenvif_get_sset_count,
@@ -231,7 +231,7 @@
 	.get_strings = xenvif_get_strings,
 };
 
-static struct net_device_ops xenvif_netdev_ops = {
+static const struct net_device_ops xenvif_netdev_ops = {
 	.ndo_start_xmit	= xenvif_start_xmit,
 	.ndo_get_stats	= xenvif_get_stats,
 	.ndo_open	= xenvif_open,