When simplifying the DoubleToI stub
(https://chromium-review.googlesource.com/c/v8/v8/+/720963), I accidentaly
removed support for generating a version of the stub which uses SSE
instructions. Re-enable support for this.

Bug: chromium:777304
Change-Id: I03c14464a2cf288216f59f59c88be7af42ef350b
Reviewed-on: https://chromium-review.googlesource.com/733130
Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48840}