USB: add a private-data pointer to struct usb_tt

For improved scheduling of transfers through a Transaction Translator,
ehci-hcd will need to store a bunch of information associated with the
FS/LS bus on the downstream side of the TT.  This patch adds a pointer
for such HCD-private data to the usb_tt structure.
Signed-off-by: NAlan Stern <stern@rowland.harvard.edu>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

include/linux/usb/hcd.h

@@ -506,6 +506,7 @@ struct usb_tt {
 	struct usb_device	*hub;	/* upstream highspeed hub */
 	int			multi;	/* true means one TT per port */
 	unsigned		think_time;	/* think time in ns */
+	void			*hcpriv;	/* HCD private data */
 
 	/* for control/bulk error recovery (CLEAR_TT_BUFFER) */
 	spinlock_t		lock;