power: qpnp-fg-gen4: Add support to read battery id from ADC channel

Add support to read battery id from ADC channel if specified with
batt_id name under FG device. Also, add a property to specify the
pull up resistor value.

Change-Id: I9486e639e411e9954d8cfd20d7ade4760b3cd2f6
Signed-off-by: Subbaraman Narayanamurthy <subbaram@codeaurora.org>