genetlink: mark families as __ro_after_init

Now genl_register_family() is the only thing (other than the
users themselves, perhaps, but I didn't find any doing that)
writing to the family struct.

In all families that I found, genl_register_family() is only
called from __init functions (some indirectly, in which case
I've add __init annotations to clarifly things), so all can
actually be marked __ro_after_init.

This protects the data structure from accidental corruption.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/tipc/netlink_compat.c b/net/tipc/netlink_compat.c
index 07b1993..e1ae8a8 100644
--- a/net/tipc/netlink_compat.c
+++ b/net/tipc/netlink_compat.c
@@ -1222,7 +1222,7 @@ static struct genl_ops tipc_genl_compat_ops[] = {
 	},
 };
 
-static struct genl_family tipc_genl_compat_family = {
+static struct genl_family tipc_genl_compat_family __ro_after_init = {
 	.name		= TIPC_GENL_NAME,
 	.version	= TIPC_GENL_VERSION,
 	.hdrsize	= TIPC_GENL_HDRLEN,
@@ -1233,7 +1233,7 @@ static struct genl_family tipc_genl_compat_family = {
 	.n_ops		= ARRAY_SIZE(tipc_genl_compat_ops),
 };
 
-int tipc_netlink_compat_start(void)
+int __init tipc_netlink_compat_start(void)
 {
 	int res;