Enable ADC support for Rock 5A, which has the following ADC channels:

Channel 0 = Boot Mode Config
Channel 1 = Recovery Key
Channel 2 = PWM Fan
Channel 3 = Headphone Hook
Channel 4 = System Input Voltage
Channel 5 = Board ID Config
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Link: https://lore.kernel.org/r/20230710165228.105983-13-sebastian.reichel@collabora.comSigned-off-by: Heiko Stuebner <heiko@sntech.de>