Define the ADC channel used for battery identification purposes so it
can be used in drivers.
Signed-off-by: Luca Weiss <luca.weiss@fairphone.com>
Link: https://lore.kernel.org/r/20230106-pm7250b-bat_id-v1-1-82ca8f2db741@fairphone.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>