ACPI: thermal: Drop redundant trip point flags

Trip point flags previously used by the driver need not be used any more
after the preceding changes, so drop them and adjust the code accordingly.

No intentional functional impact.

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