Unbinding the driver while streaming caused the driver to hang.

The cause of this was failing to use the v4l2_device release
function and the use of devm_kmalloc for the state structure.
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>