dt-bindings: iio: imu: mpu6050: Document invensense,icm20608d

ICM-20608-D differs from the other ICM-20608 variants by having
a DMP (Digital Motion Processor) core tacked on.
Despite having a different WHOAMI register, this variant is
completely interchangeable with the other ICM-20608 variants
by simply pretending the DMP core doesn't exist.

Signed-off-by: Michael Srba <Michael.Srba@seznam.cz>
Acked-by: Rob Herring <robh@kernel.org>
Reviewed-by: Krzysztof Kozlowski <krzk@kernel.org>
Link: https://lore.kernel.org/r/20220323121550.16096-2-michael.srba@seznam.cz


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