Input: gamecon - add SNES mouse support

SNES gamepads and mice share the same type of interface so they both can be
connected to the parallel port using a simple interface.  Adding mouse
support to a gamepad driver may sound funny at first, but doing so in this
case makes it possible to connect and SNES gamepads and mice at the same
time, on the same port.

Signed-off-by: Raphael Assenat <raph@raphnet.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>