ArmVirtPkg: remove PcdKludgeMapPciMmioAsCached

ArmVirtPkg: remove PcdKludgeMapPciMmioAsCached

In ARM/AARCH64 guests that run on KVM, we can now use virtio-gpu-pci, so
PcdKludgeMapPciMmioAsCached is no longer necessary. Standard VGA continues
to work on TCG without the kludge.

Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Ref: https://tianocore.acgmultimedia.com/show_bug.cgi?id=66
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>