ASCII Keyboard Controller support

[Zarithya]

Adding basic support for the ASCII Corporation Keyboard Controller peripheral for GameCube (ASC-1901PO).

[DacoTaco]

lgtm and i assume you tested it all @Zarithya ?

i have one improvement idea though, but idk if its for this PR or as a next step : integration into stdin.
the wii keyboard code can do it, and i was wondering if we couldn't get both inputs to work and integrate into a single stdin device.

thats out of my knowledge base and i'd let @WinterMute decide on how that code is best designed
would make using it very easy though

[Zarithya]

@DacoTaco It's been tested as much as I can test, having needed to give the borrowed keyboard controller back today. Fwiw I've written support for it into my controller tester and it works great. It would definitely be nice to have some stdin code but that's outside of my knowledge base too. Right now it only receives scancodes, which is less than ideal.