It's sufficient to bailout when seeing that the function literal is a
generator or async function, as those are the only cases in which there can be
yields.

Also: add a comment on --turbo-from-bytecode and Ignition generators.

R=mstarzinger@chromium.org
BUG=

Review-Url: https://codereview.chromium.org/2060843002
Cr-Commit-Position: refs/heads/master@{#36930}