V4L/DVB (6840): tuner: convert tda9887 to use TUNER_SET_CONFIG

Use TUNER_SET_CONFIG to set configuration in tda9887's private state
structure, rather than storing tda9887-specific configuration within
struct tuner.

Update handling of TUNER_SET_CONFIG by tuner-core, to call
&t->fe.ops.analog_demod_ops rather than &t->fe.ops.tuner_ops

analog_demod_ops.set_config passes the request to tuner_ops.set_config,
so this does not break other drivers.

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