ACPI: APD: Remove flags from struct apd_device_desc

The flags field is not used in anywhere, so remove it along with two
symbols related to it.

Signed-off-by: Hanjun Guo <guohanjun@huawei.com>
[ rjw: Subject and changelog edits ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>