The virt targets never use non-coherent DMA, so there is no point
in having a shared DmaLib library class resolution pointing to
ArmDmaLib. So drop it.
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>