dt-bindings: iio: adc: Add MediaTek MT6359 PMIC AUXADC

dt-bindings: iio: adc: Add MediaTek MT6359 PMIC AUXADC

Add a new binding for the MT6350 Series (MT6357/8/9) PMIC AUXADC,
providing various ADC channels for both internal temperatures and
voltages, audio accessory detection (hp/mic/hp+mic and buttons,
usually on a 3.5mm jack) other than some basic battery statistics
on boards where the battery is managed by this PMIC.

Also add the necessary dt-binding headers for devicetree consumers.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://patch.msgid.link/20240604123008.327424-2-angelogioacchino.delregno@collabora.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>