In a few places we were always looking at component 0, which obviously
doesn't go well.

Bug: b/140648938
Test: dEQP-VK.*ldexp*
Change-Id: I6a8698a56beab8ccc3b41a729d399b957cde9495
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/36113Tested-by: Chris Forbes <chrisforbes@google.com>
Presubmit-Ready: Chris Forbes <chrisforbes@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>