compositor: change weston_surface::destroy_signal argument

compositor: change weston_surface::destroy_signal argument

Pass 'this' weston_surface as the data argument to
weston_surface::destroy_signal listeners. The old &surface->resource was
really just an offsetted pointer to the weston_surface anyway. And,
because 'resource' happened to be the first member in struct weston_surface,
it was actually 'this' weston_surface.

The argument type was accidentally changed in commit
26ed73cee858956f6af07c3e4bb49b5514f17b8b from wl_resource* to
wl_resource**.

Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>