landlock: Fix kernel-doc warning for pointer-to-array parameters

landlock: Fix kernel-doc warning for pointer-to-array parameters

The insert_rule() and create_rule() functions take a
pointer-to-flexible-array parameter declared as:

  const struct landlock_layer (*const layers)[]

The kernel-doc parser cannot handle a qualifier between * and the
parameter name in this syntax, producing spurious "Invalid param" and
"not described" warnings.

Remove the const qualifier of the "layers" argument to avoid this
parsing issue.

Cc: Günther Noack <gnoack@google.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Reviewed-by: Günther Noack <gnoack3000@gmail.com>
Link: https://lore.kernel.org/r/20260310172004.1839864-1-mic@digikod.net
Signed-off-by: Mickaël Salaün <mic@digikod.net>