If "use asm" is used inside a "function*" or async function, it should
bail out.

Drive-by: Minor cleanup in {Runtime_InstantiateAsmJs}.

R=ecmziegler@chromium.org

Bug: chromium:1065852
Change-Id: Ice48126b803a30c4b4ff7b5ae22df85a3f36198a
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2126920Reviewed-by: Emanuel Ziegler <ecmziegler@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66939}