dt-bindings: iio: adc: Add rockchip,rk3562-saradc string

Add rockchip,rk3562-saradc compatible string.
The saradc on rk3562 is v2 controller, with 10bit width which is different
with rk3588.

Signed-off-by: Kever Yang <kever.yang@rock-chips.com>
Acked-by: Rob Herring (Arm) <robh@kernel.org>
Link: https://patch.msgid.link/20250227110343.2342017-1-kever.yang@rock-chips.com


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