media: vidtv: Fix memory leak in remove

vidtv_bridge_remove() releases and cleans up everything except for dvb
itself. The patch adds this missed release.

Found by Linux Driver Verification project (linuxtesting.org).

Signed-off-by: Evgeny Novikov <novikov@ispras.ru>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>