This adds support for the SARADCv2 found on RK3588.
There is no stop callback as it is currently configured in single
conversion mode, where the ADC is powered down after a single conversion
has been made.
Due to what seems to be a silicon bug, a controller reset needs to be
issued before starting a channel conversion otherwise Rockchip says that
channel 1 will error whatever that means. This is aligned with upstream
and downstream Linux kernel as well as downstream U-Boot.
Cc: Quentin Schulz <foss+uboot@0leil.net>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>
Signed-off-by: Quentin Schulz <quentin.schulz@theobroma-systems.com>
38f47eb468