thermal/debugfs: Rename thermal_debug_update_temp() to thermal_debug_update_trip_stats()

Rename thermal_debug_update_temp() to thermal_debug_update_trip_stats()
which is a better match for the purpose of the function.

No functional impact.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>
Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>