[media] tvaudio: add back lost tda9875 copyright

When the separate tda9875 driver was merged into tvaudio the copyright
line of the tda9875 driver was dropped inadvertently. Add it back.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>