usb: musb: dsps: create debugfs directory under usb root

Now the USB gadget subsystem can use the USB debugfs root directory,
so move dsps'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/1573541519-28488-6-git-send-email-chunfeng.yun@mediatek.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/musb/musb_dsps.c

@@ -411,7 +411,7 @@ static int dsps_musb_dbg_init(struct musb *musb, struct dsps_glue *glue)
 	char buf[128];
 
 	sprintf(buf, "%s.dsps", dev_name(musb->controller));
-	root = debugfs_create_dir(buf, NULL);
+	root = debugfs_create_dir(buf, usb_debug_root);
 	glue->dbgfs_root = root;
 
 	glue->regset.regs = dsps_musb_regs;