VK_SUBOPTIMAL_KHR is a success code so it should not override failure
codes, but should not get replaced by a VK_SUCCESS result itself.

Bug: b/144766511
Change-Id: Ie7721fb3afc36f0b15579deff79dc9bdc9146cd0
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/40308
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>
Tested-by: Nicolas Capens <nicolascapens@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>