staging: usbip: put usb_device and kill event handler thread in error cleanups.

If probe returns with error, the kthread is still alive even when all
usbip modules unloaded. So do cleanups in error handler.

Signed-off-by: harvey.yang <harvey.huawei.yang@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>