[media] rtl2832: add muxed I2C adapter for demod itself

There was a deadlock between master I2C adapter and muxed I2C
adapter. Implement two I2C muxed I2C adapters and leave master
alone, just only for offering I2C adapter for these mux adapters.

Reported-by: Luis Alves <ljalvs@gmail.com>
Reported-by: Benjamin Larsson <benjamin@southpole.se>
Signed-off-by: Antti Palosaari <crope@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>