USB: misc: uss720: unregister parport on probe failure

In the Linux kernel, the following vulnerability has been resolved: USB: misc: uss720: unregister parport on probe failure uss720_probe() registers a parport before reading the 1284 register used to detect unsupported Belkin F5U002 adapters. If get_1284_register() fails, the error path drops the driver private data and the USB device reference, but leaves the parport device registered. Leaving the port registered is more than a private allocation leak: parport_register_port() has already reserved a parport number and registered the parport bus device, while pp->private_data still points at the private data that the common error path is about to release. Undo the pre-announce registration in the get_1284_register() failure branch before jumping to the common private-data cleanup path. Clear priv->pp first, matching the disconnect path and avoiding a stale pointer in the private data. This issue was identified during our ongoing static-analysis research while reviewing kernel code.