dt-bindings: iio: magnetometer: asahi-kasei,ak8975: Drop deprecated enums

Drop deprecated enums from bindings as it is been here for a long time.

Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
Acked-by: Rob Herring <robh@kernel.org>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20230818075600.24277-4-biju.das.jz@bp.renesas.com


Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>