wusb: return -ENOTCONN when resetting a port with no connected device

If reading the device descriptor fails during hub_port_init() fails,
then the port is disabled, disconnecting the device.  The port is then
reset at the start of the next init attempt but there is no device to
reset.
Signed-off-by: David Vrabel <david.vrabel@csr.com>

drivers/usb/wusbcore/devconnect.c

@@ -386,6 +386,7 @@ static void __wusbhc_dev_disconnect(struct wusbhc *wusbhc,
 			  | USB_PORT_STAT_LOW_SPEED | USB_PORT_STAT_HIGH_SPEED);
 	port->change |= USB_PORT_STAT_C_CONNECTION | USB_PORT_STAT_C_ENABLE;
 	if (wusb_dev) {
+		dev_dbg(wusbhc->dev, "disconnecting device from port %d\n", wusb_dev->port_idx);
 		if (!list_empty(&wusb_dev->cack_node))
 			list_del_init(&wusb_dev->cack_node);
 		/* For the one in cack_add() */

drivers/usb/wusbcore/rh.c

@@ -100,6 +100,9 @@ static int wusbhc_rh_port_reset(struct wusbhc *wusbhc, u8 port_idx)
 	struct wusb_port *port = wusb_port_by_idx(wusbhc, port_idx);
 	struct wusb_dev *wusb_dev = port->wusb_dev;
 
+	if (wusb_dev == NULL)
+		return -ENOTCONN;
+
 	port->status |= USB_PORT_STAT_RESET;
 	port->change |= USB_PORT_STAT_C_RESET;