comedilib.h: fix a typo in a comment
comedilib.h: fix a typo in a comment

Linux-Comedi/comedilib,Linux-Comedi/comedilib,Linux-Comedi/comedilib,olsonse/comedilib,olsonse/comedilib,olsonse/comedilib,olsonse/comedilib,olsonse/comedilib,Linux-Comedi/comedilib,Linux-Comedi/comedilib,Linux-Comedi/comedilib,olsonse/comedilib