KVM: arm64: Set kvm_vcpu::pre_pcpu properly

virt inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I4BLL0


CVE: NA

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kvm_vcpu::pre_pcpu was introduced in commit bf9f6ac8 ("KVM: Update
Posted-Interrupts Descriptor when vCPU is blocked") but has so far only
been used by x86.

Set it properly on the vcpu_put() path for arm64.

Signed-off-by: Zenghui Yu <yuzenghui@huawei.com>
Reviewed-by: Cheng Jian <cj.chengjian@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>