xen-netback: use kstrdup instead of open-coding it

use kstrdup instead of open-coding it.
Reported-by: Zeal Robot <zealci@zte.com.cn>
Signed-off-by: Minghao Chi <chi.minghao@zte.com.cn>
Acked-by: Wei Liu <wei.liu@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/xen-netback/xenbus.c

@@ -865,13 +865,12 @@ static int connect_data_rings(struct backend_info *be,
 	 * queue-N.
 	 */
 	if (num_queues == 1) {
-		xspath = kzalloc(strlen(dev->otherend) + 1, GFP_KERNEL);
+		xspath = kstrdup(dev->otherend, GFP_KERNEL);
 		if (!xspath) {
 			xenbus_dev_fatal(dev, -ENOMEM,
 					 "reading ring references");
 			return -ENOMEM;
 		}
-		strcpy(xspath, dev->otherend);
 	} else {
 		xspathsize = strlen(dev->otherend) + xenstore_path_ext_size;
 		xspath = kzalloc(xspathsize, GFP_KERNEL);