KVM: arm64: Introduce shadow device

virt inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I8K8HP


CVE: NA

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The shadow device implement that establish relationships between
virtual devices and back-end virtual platform devices.

Signed-off-by: wanghaibin <wanghaibin.wang@huawei.com>
Signed-off-by: Zenghui Yu <yuzenghui@huawei.com>
Signed-off-by: Kunkun Jiang <jiangkunkun@huawei.com>
Signed-off-by: Dongxu Sun <sundongxu3@huawei.com>