iio: adc: rockchip_saradc: add rk3562

rk3562 is using v2 saradc with 8 channels.

Signed-off-by: Simon Xue <xxm@rock-chips.com>
Signed-off-by: Kever Yang <kever.yang@rock-chips.com>
Link: https://patch.msgid.link/20250227110343.2342017-2-kever.yang@rock-chips.com


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