fs/ioctl: Add a comment to keep the logic in sync with LSM policies

fs/ioctl: Add a comment to keep the logic in sync with LSM policies

Landlock's IOCTL support needs to partially replicate the list of
IOCTLs from do_vfs_ioctl().  The list of commands implemented in
do_vfs_ioctl() should be kept in sync with Landlock's IOCTL policies.

Suggested-by: Paul Moore <paul@paul-moore.com>
Suggested-by: Mickaël Salaün <mic@digikod.net>
Signed-off-by: Günther Noack <gnoack@google.com>
Link: https://lore.kernel.org/r/20240419161122.2023765-12-gnoack@google.com
Signed-off-by: Mickaël Salaün <mic@digikod.net>