rtl28xxu: attach SDR module later

SDR module was attached between demod and tuner. Change it happen
after tuner attached. We are going to implement V4L controls for
tuner drivers and those controls are loaded during SDR attach. Due to
that (tuner controls), tuner driver must be loaded before SDR module.

Also as we are here, limit SDR module loading only for those tuners
we support.

Signed-off-by: Antti Palosaari <crope@iki.fi>
e4000: implement controls via v4l2 control framework

Implement gain and bandwidth controls using v4l2 control framework.
Pointer to control handler is provided by exported symbol.

Cc: Mauro Carvalho Chehab <m.chehab@samsung.com>
Cc: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Antti Palosaari <crope@iki.fi>
rtl2832_sdr: use E4000 tuner controls via V4L framework

Use V4L2 control framework for E4000 tuner as it provides controls
that way now.

Cc: Mauro Carvalho Chehab <m.chehab@samsung.com>
Cc: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Antti Palosaari <crope@iki.fi>
e4000: remove .set_config() which was for controls

That custom DVB callback is not needed anymore for setting gain
controls as those are now implemented using V4L2 control framework.

That change was proposed by Mauro.

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