Add ACPI support for Virt Xen ARM and only for aarch64. It gets the
ACPI tables through Xen ARM multiboot protocol.
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Shannon Zhao <shannon.zhao@linaro.org>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>