usb: gadget: pxa27x: 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/1573541519-28488-11-git-send-email-chunfeng.yun@mediatek.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: Chunfeng Yun

drivers/usb/gadget/udc/pxa27x_udc.c

@@ -207,7 +207,7 @@ static void pxa_init_debugfs(struct pxa_udc *udc)
 {
 	struct dentry *root;
 
-	root = debugfs_create_dir(udc->gadget.name, NULL);
+	root = debugfs_create_dir(udc->gadget.name, usb_debug_root);
 	udc->debugfs_root = root;
 
 	debugfs_create_file("udcstate", 0400, root, udc, &state_dbg_fops);