d3d10umd: Flush on present

To ensure all submitted commands are visible on screen flush them.
Fixes tri.cpp test with softpipe.

Signed-off-by: Max Ramanouski <max8rr8@gmail.com>
Signed-off-by: Max R <max8rr8@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/36769>

src/gallium/frontends/d3d10umd/DxgiFns.cpp

@@ -61,6 +61,7 @@ _Present(DXGI_DDI_ARG_PRESENT *pPresentData)
    struct Device *device = CastDevice(pPresentData->hDevice);
    Resource *pSrcResource = CastResource(pPresentData->hSurfaceToPresent);
 
+   device->pipe->flush(device->pipe, NULL, 0);
    device->pipe->screen->flush_frontbuffer(device->pipe->screen, device->pipe, 
       pSrcResource->resource, 0, 0, pPresentData->pDXGIContext, 0, NULL);