ACPI / thermal: Fix wrong variable usage in debug statement

A debug statement in acpi_thermal_trips_update() uses a wrong trip
point (tz->trips.critical instead of tz->trips.hot) to get the
temperature value from.  Fix that.

Signed-off-by: Zhihui Zhang <zzhsuny@gmail.com>
[rjw: Subject and changelog]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>