V4L/DVB (3885): Convert dvb-pll to be a refactored tuner

Rename pll calls to appropriate tuner calls.
Remove pll functions from demod structures.
Hook tuner call into tuner_ops.
Remove BUG_ON() and convert to a soft error.

Signed-off-by: Andrew de Quincey <adq_dvb@lidskialf.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>