media: vidtv: move kfree(dvb) to vidtv_bridge_dev_release()

Adding kfree(dvb) to vidtv_bridge_remove() will remove the memory
too soon: if an application still has an open filehandle to the device
when the driver is unloaded, then when that filehandle is closed, a
use-after-free access takes place to the freed memory.

Move the kfree(dvb) to vidtv_bridge_dev_release() instead.

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Fixes: 76e21bb8 ("media: vidtv: Fix memory leak in remove")
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>