ARM: dts: aspeed: mtjade: Move all adc sensors into iio-hwmon node

Move adc14 and adc15 (battery sensor) into single iio-hwmon node to
correct label to be read by single application for all adc sensors.

Signed-off-by: Quan Nguyen <quan@os.amperecomputing.com>
Signed-off-by: Thang Q. Nguyen <thang@os.amperecomputing.com>
Reviewed-by: Joel Stanley <joel@jms.id.au>
Link: https://lore.kernel.org/r/20220228000242.1884-6-quan@os.amperecomputing.com
Signed-off-by: Joel Stanley <joel@jms.id.au>