access: disable phys-bits=36 for now

Support for guest-MAXPHYADDR < host-MAXPHYADDR is not upstream yet,
it should not be enabled.  Otherwise, all the pde.36 and pte.36
fail and the test takes so long that it times out.

Reported-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>