qpnp-fg-gen3: add support to configure jeita hysteresis

GEN3 FG has jeita hysteresis support in hardware. Add support
to configure the hysteresis applied to jeita temperature via
a device tree property.

While at it, fix reading the JEITA thresholds from device tree
property where the total size of the elements was used instead
of the total number of elements.

Change-Id: I1d468f1291224de0f781ca71cbc1374a29d7c790
Signed-off-by: Subbaraman Narayanamurthy <subbaram@codeaurora.org>