power: max17040: get thermal data from adc if available

power: max17040: get thermal data from adc if available

Since fuel gauge does not support thermal monitoring,
some vendors may couple this fuel gauge with thermal/adc
sensor to monitor battery cell exact temperature.

Add this feature by adding optional iio thermal channel.

Signed-off-by: Svyatoslav Ryhel <clamor95@gmail.com>
Reviewed-by: Iskren Chernev <me@iskren.info>
Link: https://lore.kernel.org/r/20230731073613.10394-4-clamor95@gmail.com
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>