set cpi.service as enabled in the systemd presets
    
    the cpi.service from the s390utils package replaced an older
    init script. Lets enable that by default. The previous init
    script was also enabled by deault (e.g. see
    https://src.fedoraproject.org/rpms/s390utils/blob/f23/f/cpi.initd )
    
    Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>