samples/landlock: Format with clang-format

Let's follow a consistent and documented coding style.  Everything may
not be to our liking but it is better than tacit knowledge.  Moreover,
this will help maintain style consistency between different developers.

This contains only whitespace changes.

Automatically formatted with:
clang-format-14 -i samples/landlock/*.[ch]

Link: https://lore.kernel.org/r/20220506160513.523257-8-mic@digikod.net


Cc: stable@vger.kernel.org
Signed-off-by: Mickaël Salaün <mic@digikod.net>