PCI: Make a shareable UUID for PCI firmware ACPI _DSM

The PCI Firmware Specification, r3.0, sec 4.6.4.1.3, defines a single UUID
for an ACPI _DSM method to provide device-specific control functions.  This
_DSM method support several functions, including PCI Express Slot
Information, PCI Express Slot Number, PCI Bus Capabilities, etc.

Move the UUID definition from pci/pci-label.c, where it could be used only
for one function, to pci/pci-acpi.c where it can be shared for all these
functions.

[bhelgaas: changelog]
Signed-off-by: Aaron Lu <aaron.lu@intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>