[media] r820t: remove redundant initializations in r820t_attach()

fe->tuner_priv and fe->ops.tuner_ops are initialized twice in r820t_attach().
Remove the redundant initializations and also move fe->ops.tuner_ops
initialization outside of the mutex lock (as in the xc4000 tuner code for example).

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>