Staging: comedi: fix printk issue in pcl818.c

This is a patch to the pcl818.c file that fixes up a printk
warning found by the checkpatch.pl tool

Signed-off-by: Ravishankar Karkala Mallikarjunayya <ravishankar.km@greenturtles.in>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>