Input: gamecon - clear unused function pointers

gc_parport_cb is a local uninitialized structure and the member
function pointers will be pointing to arbitrary locations unless they
are cleared.

Fixes: a517e87c3dfc ("Input: gamecon - use parallel port device model")
Signed-off-by: Sudip Mukherjee <sudip@vectorindia.org>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

drivers/input/joystick/gamecon.c

@@ -951,6 +951,7 @@ static void gc_attach(struct parport *pp)
 	pads = gc_cfg[port_idx].args + 1;
 	n_pads = gc_cfg[port_idx].nargs - 1;
 
+	memset(&gc_parport_cb, 0, sizeof(gc_parport_cb));
 	gc_parport_cb.flags = PARPORT_FLAG_EXCL;
 
 	pd = parport_register_dev_model(pp, "gamecon", &gc_parport_cb,