This change adds an input device for the Saitek X52 pro flight control
system. However, with this change, there is some bug which causes a
kernel crash. Still debugging, but committing so that I don't lose data.
With this change, the X52 USB control API is moved to it's own
file in order to better separate the code and make it cleaner.
This change also renames the kernel module to saitek_x52.
This is pretty much bare bones code to get a basic sysfs filesystem
in place. It has only code to create sysfs files for the 3 MFD lines.
Right now, this needs to be enabled by unplugging the joystick,
insmod'ing the x52joy.ko module, rmmod'ing the usbhid module and
replugging the joystick. We don't yet have a /dev/input/ interface
and there's no interrupt message handling yet.