V4L/DVB (11277): tvaudio: always call init_timer to prevent rmmod crash.

In the tvaudio_remove function del_timer_sync(&chip->wt) is called.
However, chip->wt isn't always initialized depending on the type of
audio chip. Since del_timer_sync hangs when given an uninitialized timer
we should always initialize it.

Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>