This function works with VkFormat, not spv::ImageFormat (due to input
attachments)

Change-Id: I36a36a94127533a009df8f806b55ff2845162a76
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/35528Tested-by: Chris Forbes <chrisforbes@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>