iio: adc: qcom-spmi-adc5: define ADC5_BAT_ID_100K_PU channel

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.com


Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>