wined3d: Make wined3d_swapchain_get_front_buffer_data work with wined3d_texture and sub_resource_idx.
Signed-off-by: Riccardo Bortolato <rikyz619@gmail.com>
Signed-off-by: Henri Verbeet <hverbeet@codeweavers.com>
Signed-off-by: Alexandre Julliard <julliard@winehq.org>