V4L/DVB (9619): tvaudio: update initial comments

A driver used on several bttv boards since 2000 is not experimental
anymore ;) Remove it from the comments.

While there, update copyrights addind a quick note about the "recent"
updates since 2005.

Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>