USB: EHCI: use the new usb debugfs directory

All usb debugfs files should be behind the usb directory, not at the
root of debugfs.

Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/host/ehci-hcd.c

@@ -1097,7 +1097,7 @@ static int __init ehci_hcd_init(void)
 		 sizeof(struct ehci_itd), sizeof(struct ehci_sitd));
 
 #ifdef DEBUG
-	ehci_debug_root = debugfs_create_dir("ehci", NULL);
+	ehci_debug_root = debugfs_create_dir("ehci", usb_debug_root);
 	if (!ehci_debug_root) {
 		retval = -ENOENT;
 		goto err_debug;