MAKE_VULKAN_INSTANCE_ENTRY never got undefined

Bug: b/125417927
Change-Id: I0fd5d8054748ff6279a65a5086e9a717441e583f
Reviewed-on: https://swiftshader-review.googlesource.com/c/25469Reviewed-by: Chris Forbes <chrisforbes@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>
Tested-by: Hernan Liatis <hliatis@google.com>