(define swift5-config
  (plain-file "swift5.conf"
          "options snd-intel-dspcfg dsp_driver=1"))
...
(operating-system
...
(services
  (cons*
   (simple-service 'swift5-config etc-service-type
           (list `("modprobe.d/swift5.conf"
               ,swift5-config)))
    ...
       %desktop-services))))