There's not really a point in passing the resume_mode as parameter to
the ResumeGenerator builtin. Instead we could as well just store the
mode to the generator object directly.

Drive-by-fix: On Intel allocate the generator to the new.target register
immediately so we don't need to move it there later.

Bug: v8:6344, v8:6354
Change-Id: I74e98cfffa2b3d72c43d8b6e9fdca03d01c9b4fa
Reviewed-on: https://chromium-review.googlesource.com/774259Reviewed-by: Georg Neis <neis@chromium.org>
Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49401}