power: qpnp-fg-gen4: add MSOC for slope limiting in FVSS

Currently, Vbatt_avg alone is used to calculate the SOC in
filtered voltage based SOC scaling (FVSS). This works fine
mostly. However, when the battery temperature is low and ESR
increases, MSOC calculated by HW tracks it better. SW calculated
SOC stays at the same value for a longer period because Vbatt_avg
goes high as soon as the battery temperature comes back to
normal and this impacts the user experience. Fix this by taking
in MSOC from HW into account while slope limiting the SOC.

While at it, add a separate debug mask for FVSS logs.

Change-Id: Id5d2b923ac31a28cb65dec7d3032c86e484c579c
Signed-off-by: Subbaraman Narayanamurthy <subbaram@codeaurora.org>