USB: remove OTG build warning

Somewhere along the line, a variable in a USB-OTG codepath
stopped being used; this removes the relevant compiler warning.
Signed-off-by: NDavid Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

drivers/usb/core/hub.c

@@ -1254,7 +1254,6 @@ int usb_new_device(struct usb_device *udev)
 					USB_DT_OTG, (void **) &desc) == 0) {
 			if (desc->bmAttributes & USB_OTG_HNP) {
 				unsigned		port1 = udev->portnum;
-				struct usb_device	*root = udev->parent;
 
 				dev_info(&udev->dev,
 					"Dual-Role OTG device on %sHNP port\n",