How to run the lenovo_fix_coil_whine at boot automatically
----------------------------------------------------------

See:
        https://www.linode.com/docs/guides/start-service-at-boot/

1. Make a file with this contents:

        [Unit]
        Description=Lenovo Fix By Disabling C-States Bigger Than C1

        [Service]
        Type=simple
        ExecStart=/usr/local/bin/lenovo_fix_coil_whine 250

        [Install]
        WantedBy=multi-user.target

   and put it in:

        /etc/systemd/system/lenovo_fix_coil_whine.service
        /usr/lib/systemd/system/lenovo_fix_coil_whine.service

2. Put the executable that sets the /dev/cpu_dma_latency in

        /usr/local/bin/lenovo_fix_coil_whine

3. Test with 'start' and 'stop':

        systemctl start lenovo_fix_coil_whine
        
   and:

        systemctl stop lenovo_fix_coil_whine

4. Once happy, make it able to run at boot by doing 'enable':

        systemctl enable lenovo_fix_coil_whine

   which is the equivalent of making the symlink:

        /etc/systemd/system/multi-user.target.wants/lenovo_fix_coil_whine.service

DONE!