iio: light: cm32181: Add some extra register defines

These come from a newer version of cm32181.c, which is floating around
the net, with a copyright of:

 * Copyright (C) 2014 Capella Microsystems Inc.
 * Author: Kevin Tsai <ktsai@capellamicro.com>
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2, as published
 * by the Free Software Foundation.

Note that this removes the bogus CM32181_CMD_ALS_ENABLE define, there
is no enable bit, only a disable bit and enabled is the absence of
being disabled.

This is a preparation patch for adding support for the older
CM3218 model of the light sensor.

Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>