Also jettison all the context-level perspective enable plumbing; it
serves no purpose in Vulkan.

Test: dEQP-VK.spirv_assembly.instruction.graphics.cross_stage.*
Change-Id: If823c099a82750a57bca16f04ff2ddbeee3a8f45
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/31228
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>
Tested-by: Chris Forbes <chrisforbes@google.com>
Presubmit-Ready: Chris Forbes <chrisforbes@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>