net: mark net_proto_ops as const

All usages of structure net_proto_ops should be declared const.

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/pppox.c b/drivers/net/pppox.c
index 4f6d33f..c14ee24 100644
--- a/drivers/net/pppox.c
+++ b/drivers/net/pppox.c
@@ -125,7 +125,7 @@
 	return rc;
 }
 
-static struct net_proto_family pppox_proto_family = {
+static const struct net_proto_family pppox_proto_family = {
 	.family	= PF_PPPOX,
 	.create	= pppox_create,
 	.owner	= THIS_MODULE,