Bluetooth: RFCOMM: Use DEVICE_ATTR_RO macro

Use DEVICE_ATTR_RO helper instead of plain DEVICE_ATTR,
which makes the code a bit shorter and easier to read.
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

net/bluetooth/rfcomm/tty.c

@@ -198,20 +198,22 @@ static void rfcomm_reparent_device(struct rfcomm_dev *dev)
 	hci_dev_put(hdev);
 }
 
-static ssize_t show_address(struct device *tty_dev, struct device_attribute *attr, char *buf)
+static ssize_t address_show(struct device *tty_dev,
+			    struct device_attribute *attr, char *buf)
 {
 	struct rfcomm_dev *dev = dev_get_drvdata(tty_dev);
 	return sprintf(buf, "%pMR\n", &dev->dst);
 }
 
-static ssize_t show_channel(struct device *tty_dev, struct device_attribute *attr, char *buf)
+static ssize_t channel_show(struct device *tty_dev,
+			    struct device_attribute *attr, char *buf)
 {
 	struct rfcomm_dev *dev = dev_get_drvdata(tty_dev);
 	return sprintf(buf, "%d\n", dev->channel);
 }
 
-static DEVICE_ATTR(address, 0444, show_address, NULL);
-static DEVICE_ATTR(channel, 0444, show_channel, NULL);
+static DEVICE_ATTR_RO(address);
+static DEVICE_ATTR_RO(channel);
 
 static struct rfcomm_dev *__rfcomm_dev_add(struct rfcomm_dev_req *req,
 					   struct rfcomm_dlc *dlc)