Staging: comedi: dt2801.c: off by one issue

"dac_range_table" has 5 elements.
Signed-off-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/staging/comedi/drivers/dt2801.c

@@ -472,7 +472,7 @@ static const struct comedi_lrange *dac_range_table[] = {
 
 static const struct comedi_lrange *dac_range_lkup(int opt)
 {
-	if (opt < 0 || opt > 5)
+	if (opt < 0 || opt >= 5)
 		return &range_unknown;
 	return dac_range_table[opt];
 }