KVM: nVMX: Exclude the SMP tests from the primary "vmx" testcases

The "vmx" testcase runs single-threaded, i.e. the tests are skipped
anyways.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>