ACPI 2.0 / ECDT: Enable correct ECDT initialization order

With wrong ECDT fixes reverted, it is possible to put ECDT probing before
acpi_enable_subsystem().

But the ultimate purpose of ECDT re-enabling is to put the ECDT probing
before the namespace initialization (acpi_load_tables()). This patch
achieves this with protections so that we can enable it later when all
necessary corrections are upstreamed.

Link 4: https://bugzilla.kernel.org/show_bug.cgi?id=112911


Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Tested-by: Chris Bainbridge <chris.bainbridge@gmail.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>