nstree: simplify return

node_to_ns() checks for NULL and the assert isn't really helpful and
will have to be dropped later anyway.

Link: https://patch.msgid.link/20251029-work-namespace-nstree-listns-v4-7-2e6f823ebdc0@kernel.org
Tested-by: syzbot@syzkaller.appspotmail.com
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>

kernel/nstree.c

@@ -194,11 +194,6 @@ struct ns_common *ns_tree_lookup_rcu(u64 ns_id, int ns_type)
 			break;
 	} while (read_seqretry(&ns_tree->ns_tree_lock, seq));
 
-	if (!node)
-		return NULL;
-
-	VFS_WARN_ON_ONCE(node_to_ns(node)->ns_type != ns_type);
-
 	return node_to_ns(node);
 }