FNMUL is efficient arm64 instruction, which can save 1 cycle
by optimizing FNEG(FMUL x y)) to FNMUL x y and
FMUL((FNEG x) y) to FNMUL x y

Change-Id: If25d9de1253098b17033a9d8736ff6a1c06601f3
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1572681
Commit-Queue: Georg Neis <neis@chromium.org>
Reviewed-by: Martyn Capewell <martyn.capewell@arm.com>
Reviewed-by: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#61230}