The existing code reuses the same SPIR-V variable for all descriptors mapped to
the same Vulkan binding, and applies the NonReadable decoration based on the
VKD3D_SHADER_DESCRIPTOR_INFO_FLAG_UAV_READ only. This potentially causes the
decoration to be applied twice, should two non-read descriptors be mapped to
the same variable, which isn't allowed in SPIR-V, and the validator complains.