board: amlogic: jethub j100: enable saradc in dts

Prepare to use ADC channel 1 to check the hardware revision of the board:
- add u-boot dts include with saradc node

Signed-off-by: Vyacheslav Bocharov <adeep@lexina.in>
Reviewed-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Link: https://lore.kernel.org/r/20220424082159.757622-6-adeep@lexina.in