usb_sg_cancel - stop scatter/gather i/o issued by usb_sg_wait
void usb_sg_cancel (struct usb_sg_request * io);
io request block, initialized with usb_sg_init
This stops a request after it has been started by usb_sg_wait. It can also prevents one initialized by usb_sg_init from starting, so that call just frees resources allocated to the request.