sec_battery: fix battery temperature accuracy.

-Further investigation reveals that "temp" does have the
correct temperature and "batt_temp_adc" is not the correct
temperature value.

-For some reason, that I have been unable to discover, healthd
is unable to access "temp" to get the value. Perhaps it's some
sort of permission issue or perhaps it's a timing issue.

-This patch exports the same value as "temp" to "batt_temp" and
with "temp" renamed "temp_notused" effectively fixes the
battery temperature.