While not strictly necessary (we could always calculate with the highest precision), it is a tiny amount of work to dramatically increase performance of instructions like InverseSqrt for relaxed precision types.

Bug: b/126873455
Change-Id: I42d5871a8e0886001e85fd4e16f8e6cb309236cf
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/28696Tested-by: Ben Clayton <bclayton@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>