netns: fix net_generic array leak

Signed-off-by: NAlexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/core/net_namespace.c

@@ -96,7 +96,7 @@ static void net_free(struct net *net)
 		return;
 	}
 #endif
-
+	kfree(net->gen);
 	kmem_cache_free(net_cachep, net);
 }