staging: comedi: dt2801: fix access to 2nd dio subdevice

Only 4 subdevices are allocated by this driver. The 2nd dio
subdevice is 'dev->subdevice + 3' not '... + 4'.
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/comedi/drivers/dt2801.c

@@ -532,7 +532,7 @@ static int dt2801_dio_insn_bits(struct comedi_device *dev,
 {
 	int which = 0;
 
-	if (s == dev->subdevices + 4)
+	if (s == dev->subdevices + 3)
 		which = 1;
 
 	if (data[0]) {
@@ -555,7 +555,7 @@ static int dt2801_dio_insn_config(struct comedi_device *dev,
 {
 	int which = 0;
 
-	if (s == dev->subdevices + 4)
+	if (s == dev->subdevices + 3)
 		which = 1;
 
 	/* configure */