[media] rtl2832_sdr: Realtek RTL2832 SDR driver module

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, ...).

http://thread.gmane.org/gmane.linux.drivers.video-input-infrastructure/44461



Signed-off-by: Antti Palosaari <crope@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>