ArmVirtPkg/ArmVirtQemu: switch to generic PciHostBridgeDxe
    
    Wire up the FdtPciHostBridgeLib introduced in the previous patch
    to the generic PciHostBridgeDxe implementation, and drop the special
    ArmVirtPkg version. The former's dependency on gEfiCpuIo2ProtocolGuid
    is satisfied by adding ArmPciCpuIo2Dxe.inf as well, and adding the PCD
    gArmTokenSpaceGuid.PcdPciIoTranslation as a dynamic PCD.
    
    In terms of functionality, no changes are intended.
    
    Contributed-under: TianoCore Contribution Agreement 1.0
    Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
    Reviewed-by: Laszlo Ersek <lersek@redhat.com>
    Ref: https://tianocore.acgmultimedia.com/show_bug.cgi?id=65