No depth buffer format uses quad layout currently and stencil
quad layout will soon be removed, so the depth buffer quad
layout logic can be removed.

Bug: b/144353295
Change-Id: I78ab5dbf292af2752ed1c6aea069a8079c21663f
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/38472
Presubmit-Ready: Alexis Hétu <sugoi@google.com>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>
Tested-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Chris Forbes <chrisforbes@google.com>
Reviewed-by: Antonio Maiorano <amaiorano@google.com>