HID: Add driver for ION iCade

Add a driver for the ION iCade mini arcade cabinet [1]. The device generates a
key press and release for each joystick movement or button press or release.
For example, moving the stick to the left will generate the "A" key being
pressed and then released.

A list of all the combinations is available in the iCade developer guide [2].

This driver hides all this and makes the device work as a generic joystick.

[1]: http://www.ionaudio.com/products/details/icade
[2]: http://www.ionaudio.com/downloads/iCade_Dev_Resource_v1.3.pdf



Signed-off-by: Bastien Nocera <hadess@hadess.net>
Reviewed-by: Benjamin Tissoires <benjamin.tissoires@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>