OvmfPkg: PciHostBridgeLib: install 64-bit PCI host aperture
    
    On the normal boot path (which is when PciHostBridgeDxe runs), the PCDs
    have been calculated; report the 64-bit PCI host aperture to
    PciHostBridgeDxe.
    
    In the Ia32 build, the PCD values (zeros) come directly from the DEC file,
    and this patch makes no difference.
    
    Cc: Gerd Hoffmann <kraxel@redhat.com>
    Cc: Jordan Justen <jordan.l.justen@intel.com>
    Cc: Marcel Apfelbaum <marcel@redhat.com>
    Cc: Thomas Lamprecht <t.lamprecht@proxmox.com>
    Ref: https://github.com/tianocore/edk2/issues/59
    Contributed-under: TianoCore Contribution Agreement 1.0
    Signed-off-by: Laszlo Ersek <lersek@redhat.com>