DT: iio: adc: Add CC_10001 binding documentation

Add the devicetree binding document for Cosmic Circuits 10001 ADC device.

Reviewed-by: Andrew Bresticker <abrestic@chromium.org>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Phani Movva <Phani.Movva@imgtec.com>
Signed-off-by: Naidu Tellapati <Naidu.Tellapati@imgtec.com>
Signed-off-by: Ezequiel Garcia <ezequiel.garcia@imgtec.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>