Liftoff currently does not support all asm.js code, and tier-up does
not work with lazy compilation. Hence, disable Liftoff for asm.js in
general. We will look at this later, when we have better tier-up.

R=titzer@chromium.org

Bug: v8:6600
Change-Id: I00d9e27d861067b22c0738ade7070538ee8c919c
Reviewed-on: https://chromium-review.googlesource.com/1047245Reviewed-by: Ben Titzer <titzer@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53158}