This is a leftover from the Gateway era that has long lost its utility
and that unnecessarily complicated the code base.
Please just load an external FIRM from SD card if you need something
similar.
Also refactor the multi-EmuNAND code and CTRNAND mounting code.
... even when HPs aren't inserted.
This is aimed at people using Bluetooth audio hw mods.
There are some software limitations, please read the INI/option
description.
Closes#1828.
