can: esd_usb2: use DEVICE_ATTR_RO() helper macro

Use DEVICE_ATTR_RO() helper macro instead of plain DEVICE_ATTR(), which
makes the code a bit shorter and easier to read.

Link: https://lore.kernel.org/r/20210603110902.11930-1-thunder.leizhen@huawei.comSigned-off-by: Zhen Lei <thunder.leizhen@huawei.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/usb/esd_usb2.c

@@ -474,7 +474,7 @@ static void esd_usb2_write_bulk_callback(struct urb *urb)
 	netif_trans_update(netdev);
 }
 
-static ssize_t show_firmware(struct device *d,
+static ssize_t firmware_show(struct device *d,
 			     struct device_attribute *attr, char *buf)
 {
 	struct usb_interface *intf = to_usb_interface(d);
@@ -485,9 +485,9 @@ static ssize_t show_firmware(struct device *d,
 		       (dev->version >> 8) & 0xf,
 		       dev->version & 0xff);
 }
-static DEVICE_ATTR(firmware, 0444, show_firmware, NULL);
+static DEVICE_ATTR_RO(firmware);
 
-static ssize_t show_hardware(struct device *d,
+static ssize_t hardware_show(struct device *d,
 			     struct device_attribute *attr, char *buf)
 {
 	struct usb_interface *intf = to_usb_interface(d);
@@ -498,9 +498,9 @@ static ssize_t show_hardware(struct device *d,
 		       (dev->version >> 24) & 0xf,
 		       (dev->version >> 16) & 0xff);
 }
-static DEVICE_ATTR(hardware, 0444, show_hardware, NULL);
+static DEVICE_ATTR_RO(hardware);
 
-static ssize_t show_nets(struct device *d,
+static ssize_t nets_show(struct device *d,
 			 struct device_attribute *attr, char *buf)
 {
 	struct usb_interface *intf = to_usb_interface(d);
@@ -508,7 +508,7 @@ static ssize_t show_nets(struct device *d,
 
 	return sprintf(buf, "%d", dev->net_count);
 }
-static DEVICE_ATTR(nets, 0444, show_nets, NULL);
+static DEVICE_ATTR_RO(nets);
 
 static int esd_usb2_send_msg(struct esd_usb2 *dev, struct esd_usb2_msg *msg)
 {