legacy mouse event handlers are registered in the new core,
so they receive events submitted to the new input core.

legacy kbd_mouse_event() continues to use the old code paths.
So new-core event handlers wouldn't see events submitted via
kbd_mouse_event.

This leads to the constrain that we we must transition all
kbd_mouse_event() users first to keep things working.  But
that is easier to handle than translating legacy mouse events
into new-core mouse events ;)

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>