Always enable mmiotrace when building x86 kernels
    
    mmiotrace uses the ftrace framework for dynamic patching, so enabling it
    does not cause any performance impact.
    
    Having mmiotrace enabled is very useful for debugging nvidia / nouveau
    driver problems, as we often use mmiotraces for nouveau development /
    debugging.
    
    Signed-off-by: Hans de Goede <hdegoede@redhat.com>