[d3d11] Allow UAVs to be created for the swap image

Fixes an issue with ComputeMark

src/d3d11/d3d11_present.cpp

@@ -39,7 +39,8 @@ namespace dxvk {
     desc.SampleDesc         = pSwapChainDesc->SampleDesc;
     desc.Usage              = D3D11_USAGE_DEFAULT;
     desc.BindFlags          = D3D11_BIND_RENDER_TARGET
-                            | D3D11_BIND_SHADER_RESOURCE;
+                            | D3D11_BIND_SHADER_RESOURCE
+                            | D3D11_BIND_UNORDERED_ACCESS;
     desc.CPUAccessFlags     = 0;
     desc.MiscFlags          = 0;