HID: wiimote: Add debugfs support stubs

Add initializer and deinitializer for debugfs support. This will later allow raw
eeprom access and direct DRM modifications to debug wiimote behaviour and
further protocol reverse-engineerings.

Signed-off-by: David Herrmann <dh.herrmann@googlemail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>