Staging: comedi: fix printk issue in dt3000.c

This is a patch to the dt3000.c file that fixes up a
printk warning found by the checkpatch.pl tool.

Converted printks to dev_<levels>.

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