KVM: selftests: re-map Xen's vcpu_info using HVA rather than GPA

If the relevant capability (KVM_XEN_HVM_CONFIG_SHARED_INFO_HVA) is present
then re-map vcpu_info using the HVA part way through the tests to make sure
then there is no functional change.

Signed-off-by: Paul Durrant <pdurrant@amazon.com>
Reviewed-by: David Woodhouse <dwmw@amazon.co.uk>
Link: https://lore.kernel.org/r/20240215152916.1158-16-paul@xen.org


Signed-off-by: Sean Christopherson <seanjc@google.com>