selftests/landlock: Normalize array assignment

Add a comma after each array value to make clang-format keep the
current array formatting.  See the following commit.

Automatically modified with:
sed -i 's/\t\({}\|NULL\)$/\0,/' tools/testing/selftests/landlock/fs_test.c

Link: https://lore.kernel.org/r/20220506160513.523257-5-mic@digikod.net
Cc: stable@vger.kernel.org
Signed-off-by: Mickaël Salaün <mic@digikod.net>