device/*: remove deviceinfo_nonfree

Quote from @ollieparanoid:

well, back in the day I thought it would have been nice to list exactly what is non-free about a device there. but we never ended up using it, so imho it should just be removed. we do have the nonfree firmware stuff in the device package, where we could list something similar

From: #438 (closed)

So let's get rid of it, bois!