ArmVirtPkg/FdtPciPcdProducerLib: add handling of PcdPciIoTranslation
    
    Add handling of the PcdPciIoTranslation PCD, so that modules that include
    this library via NULL resolution are guaranteed that it will be set before
    they reference it.
    
    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