Add IOCTL support to the Landlock sample tool.

The IOCTL right is grouped with the read-write rights in the sample
tool, as some IOCTL requests provide features that mutate state.
Signed-off-by: Günther Noack <gnoack@google.com>
Link: https://lore.kernel.org/r/20240419161122.2023765-9-gnoack@google.comSigned-off-by: Mickaël Salaün <mic@digikod.net>