V4L/DVB (6783): tuner: combine set_tv_freq and set_radio_freq into a single set_params method

We can tell whether we are tuning television or radio by testing for
struct analog_parameters *params->mode == V4L2_TUNER_RADIO

There is no longer any need for separate set_tv_freq and
set_radio_freq functions in the analog tuner demodulator modules.

Signed-off-by: Michael Krufky <mkrufky@linuxtv.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>