As far as I can tell these were unused; their only callers were arm
and ppc simulators, but codegen explicitly returned nullptr if in a
simulator build, falling back to std::sqrt.

There's more potential cleanup to be done here for other functions
defined in codegen-*.cc files.

Tbr: clemensh@chromium.org
Bug: v8:7777, v8:8675
Change-Id: I4b9d6062c6724a810ab094d09e3cd04a0b733d9b
Reviewed-on: https://chromium-review.googlesource.com/c/1405851Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58740}