dt-bindings: iio: adc: Add GPADC for Allwinner H616

Add support for the GPADC for the Allwinner H616. It is identical to
the existing ADC for the D1/T113s/R329/T507 SoCs.

Signed-off-by: Chris Morgan <macromorgan@hotmail.com>
Acked-by: Rob Herring (Arm) <robh@kernel.org>
Link: https://lore.kernel.org/r/20240417170423.20640-3-macroalpha82@gmail.com


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