dt-bindings: iio: adc: Add rockchip,rk3576-saradc string

Add rockchip,rk3576-saradc compatible string.
The saradc on RK3576 is compatible with the one on RK3588, so they are
used together in an arm of the oneOf.

Signed-off-by: Detlev Casanova <detlev.casanova@collabora.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Acked-by: Heiko Stuebner <heiko@sntech.de>
Link: https://patch.msgid.link/20240802214612.434179-5-detlev.casanova@collabora.com


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