Capture the per-vCPU GPA in perf_test_vcpu_args so that tests can get
the GPA without having to calculate the GPA on their own.

No functional change intended.
Signed-off-by: NSean Christopherson <seanjc@google.com>
Reviewed-by: NBen Gardon <bgardon@google.com>
Signed-off-by: NDavid Matlack <dmatlack@google.com>
Message-Id: <20211111000310.1435032-7-dmatlack@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>