Revert "ACPICA: FADT support cleanup"

Pavel Machek reports that commit 6ea8c546 (ACPICA: FADT support
cleanup) breaks thermal management on his Thinkpad X60 and T40p, so
revert it.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=187311


Fixes: 6ea8c546 (ACPICA: FADT support cleanup)
Reported-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>