A couple patches on 2.5.41; issues discovered during QA.

1: The hack to get around the unlinking bug. You said this was also in
2.5.x, so I've included this.

2: filp is NULL when called from usb_serial_disconnect. Fixes an oops.

3: In the case where the module is reloaded; the endpoints in the
usbsubsystem don't go away. So when the module comes back, the
endpoints still have the unlink thing, and also need to be cleared.
Otherwise the firmware appears not respond to the version nubmer query
and the driver doesn't attach, and you have no device.