V4L/DVB (3378): Fix for lack of analog output on some cx88 boards

- Workaround to fix a known regression at cx88-tvaudio.c
- provide a module parameter workaround to always enable
analog output.

Signed-off-by: Panagiotis Christeas <p_christ@hol.gr>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>