xwayland: Use the pixmap release callback with EGLStream
Commit 77658741 - "xwayland: Add buffer release callback" added an API to deal with Wayland buffer release callbacks.
The EGLstream implementation has its own wl_buffer callback, move that to the buffer release API instead so we don't have to deal with Wayland buffers directly and match the other Xwayland pixmap backend implementations.
Signed-off-by: Olivier Fourdan ofourdan@redhat.com
cc @ajax