power: bq25890: add POWER_SUPPLY_PROP_TEMP

Add the POWER_SUPPLY_PROP_TEMP and a NTC 10K percent VREGN to degrees LUT.

Make sure that a conversion is forced when the power supply is offline so
the temperature is valid.

Signed-off-by: Angus Ainslie <angus@akkea.ca>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>