drop_monitor: make genl_multicast_group const

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/core/drop_monitor.c b/net/core/drop_monitor.c
index d6b3b57..72cfb0c 100644
--- a/net/core/drop_monitor.c
+++ b/net/core/drop_monitor.c
@@ -105,7 +105,7 @@
 	return skb;
 }
 
-static struct genl_multicast_group dropmon_mcgrps[] = {
+static const struct genl_multicast_group dropmon_mcgrps[] = {
 	{ .name = "events", },
 };