wii - char driver for gba / joybus devices

[gummybuns]

Overview

• Adds /dev/gcport* char drivers to the nintendo wii to support additional devices on the gamecube controller ports.
• dynamically identifies gamecube controller attach / detach events through the hardware interrupt
  Working example of it can be found here

changes

• creates a driver hierarchy: si -> gcport -> uhid. uhid is only used if a gamecube controller is identified
• moves the register definitions out of si.c into si.h
• implements a queue for interfacing with sicomcsr
• always poll all four channels. use the interrupt to identify if an attach/detach event.
• use the hardware interrupt to identify tcint events. dequeue transactions upon completion
• adds the child driver gcport_si.c with an ioctl command to leverage the serial communication
• adds workqueue to attach/detach uhid. uhid match function checks if the physical device is a gamecube controller
• adds /dev/gcport* as a device parent to uhid