power: qpnp-fg-gen4: Add support for slope limiter configuration

Add support to configure the slope limiter coefficients based on
battery temperature and charging status. This helps with tuning
the state of charge (SOC) accuracy.

While at it, print monotonic SOC instead of the capacity shown by
FG driver and cache the battery temperature during driver probe.

Change-Id: I64af892ac5973bb95d66c6aa20c0af6d39b31f94
Signed-off-by: Subbaraman Narayanamurthy <subbaram@codeaurora.org>