dt-bindings: iio: imu: st_lsm6dsx: add lsm6dsv16x

Add device bindings for lsm6dsv16x IMU sensor.
Use lsm6dsv as fallback device for lsm6dsv16x since it implements all the
features currently supported by lsm6dsv16x.

Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/8d10a63ec6abd22863ab25addd8c2f578dbc9cd9.1667745215.git.lorenzo@kernel.org
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>