layers: GH644 Validate DS image aspect bit restriction
layers: GH644 Validate DS image aspect bit restriction

If a DS image is used in a descriptor, regardless of the underlying
image layout, we need to validate that BOTH DEPTH and STENCIL aspect
bits are NOT set. Only one of the two bits is allowed.

elongbug/Vulkan-LoaderAndValidationLayers,KhronosGroup/Vulkan-LoaderAndValidationLayers,elongbug/Vulkan-LoaderAndValidationLayers,KhronosGroup/Vulkan-LoaderAndValidationLayers,KhronosGroup/Vulkan-LoaderAndValidationLayers,KhronosGroup/Vulkan-LoaderAndValidationLayers,elongbug/Vulkan-LoaderAndValidationLayers,elongbug/Vulkan-LoaderAndValidationLayers