SetupRoutine uses V0 == V1 == V2 when drawing points, so we don't have
to duplicate those vertices explicitly.

Bug: b/149537975
Change-Id: I723a7139f5eb5735bedb0c17796c00dc4b414fa7
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/42028
Presubmit-Ready: Nicolas Capens <nicolascapens@google.com>
Tested-by: Nicolas Capens <nicolascapens@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>