ACPI: thermal_lib: Add functions returning temperature in deci-Kelvin

Because the ACPI thermal driver generally operates temperature values
in deci-Kelvin, it needs the library functions returning temperature
for various trip point types to use deci-Kelvin too.

To address that, arrange the ACPI thermal library code in three levels
of functions where the high-level ones will return temperature in
milli-Celsius, as needed by the thermal core and the majority of
thermal drivers, the mid-level ones will return temperature in
deci-Kelvin and will be called internally by the corresponding high-
level functions, and all of the mid-level functions will call the same
low-level one, acpi_trip_temp(), to actually evaluate ACPI objects to
retrieve themperature values from the platform firmware.

Going forward, this will allow the ACPI thermal driver to use the
mid-level functions to provide temperature values needed by it, so as
to reduce code duplication related to evaluating trip temperature ACPI
control methods.

No intentional functional impact.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>