staging: octeon-usb: clean up hcpriv usage

Use ep->hcpriv for pipe handle and urb->hcpriv for submit handle,
instead of packing both into the same field.

Signed-off-by: Aaro Koskinen <aaro.koskinen@iki.fi>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>