From: Ronald Bultje <rbultje@ronald.bitfreak.net>

This patch adds a release callback which frees the video_device struct.
This is needed to prevent freeing memory before it's not in use anymore,
as described in http://lwn.net/Articles/36850/. Without this, the driver
will give a warning when loaded. It might crash when unloading (see
article), too. The video4linux patch (by Gerd Knorr) was accepted a week
(or 2?) ago, but I forgot to adapt my driver to it.