power: qpnp-qg: Update the PON SOC flow

The shutdown SOC is rejected if the battery-temperature
changes beyond a threshold value. However, this check
only makes sense at low-temperatures (< 0 degrees C) where
RBAT variation is significant. Add this additional check.

While at it, apply the additional PON_OCV checks only
for PMI632.

Change-Id: I1623d1a83d4ffd175c4ce0169b3433532b882e8e
Signed-off-by: Anirudh Ghayal <aghayal@codeaurora.org>