Implement SDR driver for Realtek RTL2832U chip as a DVB extension
module. SDR module is attached by DVB USB RTL28XXU driver as a DVB
SEC (satellite equipment controller) module. Abusing unused SEC here
has no harm as that is DVB-T only frontend.
SDR functionality is provided by RTL2832 DVB-T demodulator. I suspect
it is originally planned for DAB and FM, but it could be abused general
SDR, due to modern silicon tuners that has wide frequency range and a
lot of configurable parameters (filters, gains, ...).