staging: comedi: hwdrv_apci3501: refactor apci3501_read_insn_timer()

The handling of the ADDIDATA_WATCHDOG and ADDIDATA_TIMER is identical.
Refactor this function to use a common code path for both timer modes.

Remove the incorrect dev_err() noise. The subdevice is valid but the
timer_mode is not supported.
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/comedi/drivers/addi-data/hwdrv_apci3501.c

@@ -133,19 +133,12 @@ static int apci3501_read_insn_timer(struct comedi_device *dev,
 {
 	struct apci3501_private *devpriv = dev->private;
 
-	if (devpriv->timer_mode == ADDIDATA_WATCHDOG) {
-		data[0] = inl(dev->iobase + APCI3501_TIMER_STATUS_REG) & 0x1;
-		data[1] = inl(dev->iobase + APCI3501_TIMER_SYNC_REG);
-	}
+	if (devpriv->timer_mode != ADDIDATA_TIMER &&
+	    devpriv->timer_mode != ADDIDATA_WATCHDOG)
+		return -EINVAL;
 
-	else if (devpriv->timer_mode == ADDIDATA_TIMER) {
-		data[0] = inl(dev->iobase + APCI3501_TIMER_STATUS_REG) & 0x1;
-		data[1] = inl(dev->iobase + APCI3501_TIMER_SYNC_REG);
-	}
+	data[0] = inl(dev->iobase + APCI3501_TIMER_STATUS_REG) & 0x1;
+	data[1] = inl(dev->iobase + APCI3501_TIMER_SYNC_REG);
 
-	else if (devpriv->timer_mode != ADDIDATA_TIMER &&
-		 devpriv->timer_mode != ADDIDATA_WATCHDOG) {
-		dev_err(dev->class_dev, "Invalid subdevice.\n");
-	}
 	return insn->n;
 }