netfilter: nf_tables: release flowtable hooks

Otherwise we leak this array.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nf_tables_api.c

@@ -5423,6 +5423,7 @@ static void nf_tables_flowtable_notify(struct nft_ctx *ctx,
 static void nf_tables_flowtable_destroy(struct nft_flowtable *flowtable)
 {
 	cancel_delayed_work_sync(&flowtable->data.gc_work);
+	kfree(flowtable->ops);
 	kfree(flowtable->name);
 	flowtable->data.type->free(&flowtable->data);
 	rhashtable_destroy(&flowtable->data.rhashtable);