The spec for VkDescriptorSetLayoutBinding states that
"If descriptorCount is zero this binding entry is reserved and the
resource must not be accessed from any stage via this binding within any
pipeline using the set layout."

This restores the debug validation that existed at https://swiftshader-review.googlesource.com/c/SwiftShader/+/44308/4/src/Pipeline/SpirvShaderMemory.cpp#b405

Bug: b/157915024
Change-Id: I5e6798b0cc87f564a3c6f13963995822660b5111
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/45468Tested-by: Nicolas Capens <nicolascapens@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>
Kokoro-Result: kokoro <noreply+kokoro@google.com>