qpnp-fg-gen3: Read debug battery id thresholds from RR_ADC registers

Currently, GEN3 FG driver uses a debug battery id threshold of
7 KOhms. However, depending on the battery id chosen by the user
this threshold can be modified in the bootloader. Hence, add
support to read the debug battery id thresholds directly from
RR_ADC peripheral registers. This can be used to decide whether
a fake battery SOC (67) can be displayed to the user.

Change-Id: I22ab702e10c310e4f847c6c81a48a8f0f3188429
Signed-off-by: Subbaraman Narayanamurthy <subbaram@codeaurora.org>