genetlink: only pass array to genl_register_family_with_ops()

As suggested by David Miller, make genl_register_family_with_ops()
a macro and pass only the array, evaluating ARRAY_SIZE() in the
macro, this is a little safer.

The openvswitch has some indirection, assing ops/n_ops directly in
that code. This might ultimately just assign the pointers in the
family initializations, saving the struct genl_family_and_ops and
code (once mcast groups are handled differently.)

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/l2tp/l2tp_netlink.c b/net/l2tp/l2tp_netlink.c
index 57db66e..4cfd722 100644
--- a/net/l2tp/l2tp_netlink.c
+++ b/net/l2tp/l2tp_netlink.c
@@ -887,13 +887,8 @@
 
 static int l2tp_nl_init(void)
 {
-	int err;
-
 	pr_info("L2TP netlink interface\n");
-	err = genl_register_family_with_ops(&l2tp_nl_family, l2tp_nl_ops,
-					    ARRAY_SIZE(l2tp_nl_ops));
-
-	return err;
+	return genl_register_family_with_ops(&l2tp_nl_family, l2tp_nl_ops);
 }
 
 static void l2tp_nl_cleanup(void)