Divide Dref by the projection coordinate.

The SPIR-V spec states that
"Dref /q is the depth-comparison reference value."

Bug b/129523279
Tests: dEQP-VK.glsl.texture_functions.textureproj.*
Change-Id: Ib1c4ad09f829b84b6b1065ff604fe88f8b1c1426
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/31693
Presubmit-Ready: Nicolas Capens <nicolascapens@google.com>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>
Reviewed-by: Chris Forbes <chrisforbes@google.com>
Tested-by: Nicolas Capens <nicolascapens@google.com>