comedi: ni_atmio: avoid warning for unused device_ids[] table

comedi: ni_atmio: avoid warning for unused device_ids[] table

When the driver is built-in, it produces a W=1 warning:

drivers/comedi/drivers/ni_atmio.c:209:35: error: 'device_ids' defined but not used [-Werror=unused-const-variable=]
  209 | static const struct pnp_device_id device_ids[] = {

The actual probe() function has a different way of identifying
the hardware, so just mark this one as __maybe_unused so it
can be dropped when built-in.

Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/20250409122314.2848028-8-arnd@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>