Several cleanups:
- unify identical macro defintions
- use existing macros instead of duplicating the code
- add AVX versions for xorps and xorpd (to be used by Liftoff)

R=mstarzinger@chromium.org

Bug: v8:7310, v8:6600
Change-Id: Id37c58cf6187533ad9d4a0ca8bc5d49f9de66785
Reviewed-on: https://chromium-review.googlesource.com/937124Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#51597}