d3d12: ensure resources are actually in the stream-out state

If we don't use the pre-draw flag here, we won't end up transitioning
these until some time after the draw, which isn't what we want.

src/gallium/drivers/d3d12/d3d12_draw.cpp

@@ -678,9 +678,9 @@ d3d12_draw_vbo(struct pipe_context *pctx,
       }
 
       d3d12_transition_resource_state(ctx, so_buffer, D3D12_RESOURCE_STATE_STREAM_OUT,
-                                      SubresourceTransitionFlags::SubresourceTransitionFlags_None);
+                                      SubresourceTransitionFlags_TransitionPreDraw);
       d3d12_transition_resource_state(ctx, fill_buffer, D3D12_RESOURCE_STATE_STREAM_OUT,
-                                      SubresourceTransitionFlags::SubresourceTransitionFlags_None);
+                                      SubresourceTransitionFlags_TransitionPreDraw);
    }
    if (ctx->cmdlist_dirty & D3D12_DIRTY_STREAM_OUTPUT)
       ctx->cmdlist->SOSetTargets(0, 4, so_buffer_views);