phy: phy-twl4030-usb: 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 <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Vinod Koul <[e-mail]>

drivers/phy/ti/phy-twl4030-usb.c

···
 	return 0;
 }
 
-static ssize_t twl4030_usb_vbus_show(struct device *dev,
-		struct device_attribute *attr, char *buf)
+static ssize_t vbus_show(struct device *dev,
+			 struct device_attribute *attr, char *buf)
 {
 	struct twl4030_usb *twl = dev_get_drvdata(dev);
 	int ret = -EINVAL;
···
 
 	return ret;
 }
-static DEVICE_ATTR(vbus, 0444, twl4030_usb_vbus_show, NULL);
+static DEVICE_ATTR_RO(vbus);
 
 static irqreturn_t twl4030_usb_irq(int irq, void *_twl)
 {