ACPI: bind workqueues to CPU 0 to avoid SMI corruption

On some machines, a software-initiated SMI causes corruption unless the
SMI runs on CPU 0.  An SMI can be initiated by any AML, but typically it's
done in GPE-related methods that are run via workqueues, so we can avoid
the known corruption cases by binding the workqueues to CPU 0.

References:
    http://bugzilla.kernel.org/show_bug.cgi?id=13751
    https://bugs.launchpad.net/bugs/157171
    https://bugs.launchpad.net/bugs/157691

Signed-off-by: Bjorn Helgaas <bjorn.helgaas@hp.com>
Signed-off-by: Len Brown <len.brown@intel.com>