egl/wayland: use the destroy_window_callback for swrast

egl/wayland: use the destroy_window_callback for swrast

As described in commit 690ead4a135 ("egl/wayland-egl: Fix for segfault
in dri2_wl_destroy_surface.") if we attempt to destroy a EGL surface
attached to already destroyed Wayland window we'll get a segfault.

v2: set the correct callback alongside the window->private. (Dan)

Cc: Daniel Stone <daniels@collabora.com>
Cc: "12.0 13.0" <mesa-stable@lists.freedesktop.org>
Signed-off-by: Emil Velikov <emil.velikov@collabora.com>
Reviewed-by: Daniel Stone <daniels@collabora.com>