thermal: consistently use int for trip temp

The commit 17e8351a

 consistently use int for temperature,
however it missed a few in trip temperature and thermal_core.

In current codes, the trip->temperature used "unsigned long"
and zone->temperature used"int", if the temperature is negative
value, it will get wrong result when compare temperature with
trip temperature.

This patch can fix it.

Signed-off-by: Wei Ni <wni@nvidia.com>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>