onnxruntime

daef1339 - update onnxruntime_perftest's README.md as vitisai is supported on v1.15.1 (#16827)

update onnxruntime_perftest's README.md as vitisai is supported on v1.15.1 (#16827) ### Description <!-- Describe your changes. --> Updating README.md to add vitisai for onnxruntime_perftest ### Motivation and Context <!-- - Why is this change required? What problem does it solve? --> The perftest tool does support vitisai whereas the README.md does not list it. This creates some confusions internally about if vitisai is supported. See https://github.com/microsoft/onnxruntime/pull/15673 for context.