ArmVirtPkg: Add kvmtool platform driver

ArmVirtPkg: Add kvmtool platform driver

Kvmtool is a virtual machine manager that enables
hosting KVM guests. It essentially provides a
virtual hardware platform for guest operating
systems.

Kvmtool hands of a device tree containing the
current hardware configuration to the firmware.

A standards-based operating system would use
ACPI to consume the platform hardware
information, while some operating systems may
prefer to use Device Tree.

The KvmtoolPlatformDxe performs the platform
actions like determining if the firmware should
expose ACPI or the Device Tree based hardware
description to the operating system.

Signed-off-by: Sami Mujawar <sami.mujawar@arm.com>
Acked-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@arm.com>