KVM_CAP_HYPERV_DIRECT_TLBFLUSH is only reported when KVM runs on top of
Hyper-V and hyperv_evmcs/hyperv_svm_test don't need that, these tests check
that the feature is properly emulated for Hyper-V on KVM guests. There's no
corresponding CAP for that, the feature is reported in
KVM_GET_SUPPORTED_HV_CPUID.

Hyper-V specific CPUIDs are not reported by KVM_GET_SUPPORTED_CPUID,
implement dedicated kvm_hv_cpu_has() helper to do the job.

Fixes: 6dac1195 ("KVM: selftests: Make Hyper-V tests explicitly require KVM Hyper-V support")
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Link: https://lore.kernel.org/r/20240816130139.286246-3-vkuznets@redhat.comSigned-off-by: Sean Christopherson <seanjc@google.com>