Add `R828D` tuner

[ccostes]

There are some (mostly minor) differences between the R820T and R828D - search for R828D in the osmocom library.

[tkj666]

Should we make R828D a seperate tuner or merge R820T and R828D into one R82XX like what osmocom does?

[ccostes]

It's been awhile since I've been in this code but I think I separated things out a bit more than osmocom to make it easier to understand, but if you want to take a shot at implementing it and think it makes more sense to keep them together that works for me!

[jgraef]

The tuner code has been merged, so this should be closed, right?

I have a Blog v4 and tried the rtl_tcp example with SDR++ switching between rtl_tcp input and normal (direct USB) and it doesn't match up at all. Signals are not in the right places. I will investigate this and open another issue.