ArmVirtPkg/ArmVirtPL031FdtClientLib: unconditionally disable DT node
    
    Disable the PL031 RTC DT node unconditionally rather than only when
    the DT will be exposed to the OS. This allows us to defer the decision
    whether to expose it to the OS to a later time without creating an
    additional dependency on the FDT client code by the RTC driver.
    
    Contributed-under: TianoCore Contribution Agreement 1.0
    Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
    Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>
    Reviewed-by: Laszlo Ersek <lersek@redhat.com>