media: usb: go7007: s2250-board: add missed i2c_unregister_device

The driver forgets to call i2c_unregister_device in remove like what is
done in probe failure.
Add the missed call to fix it.

Signed-off-by: Chuhong Yuan <hslester96@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>