[media] r820t: do not double-free fe->tuner_priv in r820t_release()

fe->tuner_priv is already freed by hybrid_tuner_release_state().

Signed-off-by: Gianluca Gennari <gennarone@gmail.com>
Signed-off-by: Michael Krufky <mkrufky@linuxtv.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>