Expansion port support

[Brianvgplayer]

There currently isn't an option to directly use a controller from the FC Expansion port. There is support for some specific controllers, but some behavior is closer to a controller in port 2 of the NES. A controller plugged in through the passthrough on the 3D adapter when it's connected to SNAC with the option for 3D adapter selected is detected as controller 1 and controllers have to be swapped to use the USB controller. There is currently no way to play some FC games in 4 player on MiSTer.