fs: simplify error handling

Rely on cleanup helper and simplify error handling

Link: https://lore.kernel.org/r/20240607-vfs-listmount-reverse-v1-3-7877a2bfa5e5@kernel.org


Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>