icnss: Add changes to enable VBATT feature

Power voting need to be controlled based on the battery voltage,
Register ADC and IIO channels to monitor the battery voltage,
Register threshold notification with the ADC, to get voltage
change notification based on the configuration, Register IIO
channel to read current battery voltage, if the voltage is
exceeding the predefined threshold, then update the voltage
to the firmware using QMI command.

Change-Id: I59cad3d3e301423c8a988ff34fb2db749c85c3fd
Signed-off-by: Sandeep Singh <sandsing@codeaurora.org>