KVM: arm64: Only probe Hisi ncsnp feature on Hisi CPUs

virt inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I5WHHV


CVE: NA

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The "ncsnp" is an implementation specific CPU virtualization
feature on Hisi 1620 series CPUs. This feature works just
like ARM standard S2FWB to reduce some cache management
operations in virtualization.

Given that it's Hisi specific feature, let's restrict the
detection only to Hisi CPUs. To realize this:
1) Add a sub-directory `hisilicon/` within arch/arm64/kvm to
hold code for Hisi specific virtualization features.
2) Add a new kconfig option `CONFIG_KVM_HISI_VIRT` for users
to select the whole Hisi specific virtualization features.
3) Add a generic global KVM variable `kvm_ncsnp_support`
which is `false` by default. Only re-initialize it when
we have `CONFIG_KVM_HISI_VIRT` enabled.

Signed-off-by: Yanan Wang <wangyanan55@huawei.com>
Reviewed-by: Zenghui Yu <yuzenghui@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>