usb: gadget: udc: renesas_usb3: create debugfs directory under usb root

Now the USB gadget subsystem can use the USB debugfs root directory,
so move it's directory from the root of the debugfs filesystem into
the root of usb

Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
Link: https://lore.kernel.org/r/1573541519-28488-10-git-send-email-chunfeng.yun@mediatek.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: Chunfeng Yun

drivers/usb/gadget/udc/renesas_usb3.c

@@ -2536,7 +2536,7 @@ static const struct file_operations renesas_usb3_b_device_fops = {
 static void renesas_usb3_debugfs_init(struct renesas_usb3 *usb3,
 				      struct device *dev)
 {
-	usb3->dentry = debugfs_create_dir(dev_name(dev), NULL);
+	usb3->dentry = debugfs_create_dir(dev_name(dev), usb_debug_root);
 
 	debugfs_create_file("b_device", 0644, usb3->dentry, usb3,
 			    &renesas_usb3_b_device_fops);