mfd: timberdale: Use DEVICE_ATTR_RO macro

Use DEVICE_ATTR_RO macro helper instead of plain DEVICE_ATTR, which makes
the code a bit shorter and easier to read.
Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

drivers/mfd/timberdale.c

@@ -623,8 +623,8 @@ static const struct mfd_cell timberdale_cells_bar2[] = {
 	},
 };
 
-static ssize_t show_fw_ver(struct device *dev, struct device_attribute *attr,
-	char *buf)
+static ssize_t fw_ver_show(struct device *dev,
+			   struct device_attribute *attr, char *buf)
 {
 	struct timberdale_device *priv = dev_get_drvdata(dev);
 
@@ -632,7 +632,7 @@ static ssize_t show_fw_ver(struct device *dev, struct device_attribute *attr,
 		priv->fw.config);
 }
 
-static DEVICE_ATTR(fw_ver, S_IRUGO, show_fw_ver, NULL);
+static DEVICE_ATTR_RO(fw_ver);
 
 /*--------------------------------------------------------------------------*/