thermal: intel: processor_thermal_device_pci: Use generic trip point

Make proc_thermal_pci_probe() register the TCPU_PCI thermal zone along
with the trip point used by it and drop the zone callbacks related to
this trip point that are not needed any more.

Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
[ rjw: Subject and changelog edits ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>