USB: add usb debugfs directory

Add a common usb directory in debugfs that the usb subsystem can use.

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

diff --git a/include/linux/usb.h b/include/linux/usb.h
index 3aa2cd1..29060da 100644
--- a/include/linux/usb.h
+++ b/include/linux/usb.h
@@ -1558,6 +1558,9 @@
 #define err(format, arg...) printk(KERN_ERR KBUILD_MODNAME ": " \
 	format "\n" , ## arg)
 
+/* debugfs stuff */
+extern struct dentry *usb_debug_root;
+
 #endif  /* __KERNEL__ */
 
 #endif