thermal: ACPI: Include the right header file

thermal: ACPI: Include the right header file

It is not necessary to include thermal_core.h into thermal_acpi.c,
because none of the code in there depends on anything in the former,
except for the linux/thermal.h, but it is better to include that one
directly instead of including the entire thermal_core.h, so make that
change.

No functional impact.

Fixes: 7a0e39748861 ("thermal: ACPI: Add ACPI trip point routines")
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>