In mainline Linux these paths will be used, move the firmware packaging
there. By doing this we drop downstream support. Support could be
restored by adding some symlinks in a downstream-specific package if
required.
We also start squashing the firmware into .mbn format with pil-squasher.
For now we keep the files in _wififiles in their old location, I'm not
sure yet where they need to go since I didn't have wcnss working on
mainline yet.