[media] vivid: use v4l2_device.release to clean up the driver

Use the release callback of the v4l2_device to clean up the memory.
This prevents vivid from breaking if someone tries to unbind the
driver.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>