ACPI: processor: restrict early _PDC to opt-in platforms

Commit 78f16996

 (ACPI: processor: call _PDC early) blindly walks
the namespace and calls _PDC on every processor object it finds.

This change may cause issues on platforms that declare dummy
values for SSDTs on non-present processors (disabled in MADT).
When we call _PDC and dynamically attempt to execute the AML
Load() op on these dummy SSDTs, there's no telling what might
happen.

Rather than finding every platform that has bogus SSDTs, restrict
early _PDC calls to platforms that are known to need early
evaluation of _PDC.

This is a minimal, temporary fix (given the context of the
current release cycle). A real solution of checking the MADT for
non-present processors will be written for the next merge window.

References:

	http://bugzilla.kernel.org/show_bug.cgi?id=14710
	http://bugzilla.kernel.org/show_bug.cgi?id=14954

Signed-off-by: Alex Chiang <achiang@hp.com>
Signed-off-by: Len Brown <len.brown@intel.com>