Add sdparm SCSI command utility

[tobias . geerinckx . rice]

Hullo all,

Behold my first patch submission to GNU Guix. \o/ Much wow.

I've tried to follow the manual 's best I can, ran `guix lint` and
confirmed that everything works. I'm also assuming that expanding 
terms like SCSI and IDE would add little value. (?)

It's also a very simple package.

That said, these are the first Lisp lines of my life (and, hopefully, of
many) so I'd not be surprised if I missed something. Or several.

Kind regards,

T G-R