power: qcom-charger: add driver for GEN3 fuel gauge

GEN3 FG (fuel gauge) is a new hardware peripheral which cannot
be supported along with existing GEN1/GEN2 FG supported under
qpnp-fg.c. Some of the differences are listed below.

- No conventional memory access for accessing SRAM
- No OTP region for battery profile
- FTRIM registers will be loaded to SRAM
- SRAM partitioning and address format got changed completely
- Battery id detection done by RR_ADC
- Encoding/Decoding changes for battery parameters

Hence add a new driver to support this GEN3 FG. This driver
reads the battery parameters like voltage, current, temperature,
resistance etc. acquired by the FG hardware and expose to the
userspace through a power supply class device.

Change-Id: Ibcd6e49c7dc7c3520527bcf9553296e846fb7458
Signed-off-by: Subbaraman Narayanamurthy <subbaram@codeaurora.org>