landlock: Use scoped guards for ruleset in landlock_add_rule()

Simplify error handling by replacing goto statements with automatic
calls to landlock_put_ruleset() when going out of scope.

This change depends on the TCP support.

Cc: Konstantin Meskhidze <konstantin.meskhidze@huawei.com>
Cc: Mikhail Ivanov <ivanov.mikhail1@huawei-partners.com>
Reviewed-by: Günther Noack <gnoack@google.com>
Link: https://lore.kernel.org/r/20250113161112.452505-3-mic@digikod.net


Signed-off-by: Mickaël Salaün <mic@digikod.net>