Compositor: Extend QWaylandSurfaceNode from QSGSimpleTextureNode

Use the convenience base class to remove replicated code and make use
of QSGTextureMaterial's internal optimizations.

Change-Id: I37e2728eeb62f8cc52ea22c3cc4057d63f948c9b
Reviewed-by: Gunnar Sletta <gunnar.sletta@digia.com>
Reviewed-by: Andy Nichols <andy.nichols@digia.com>