Since we create the asm offset table ourselves, we can skip all decoder
error checks when decoding it. We keep DCHECKs though to catch errors
early and give fuzzers a change to find inconsistencies in our encoding
and decoding.

R=jkummerow@chromium.org

Bug: chromium:667678
Change-Id: I2c77f3857548057ce5c432d1c6f5576d66ca5cd1
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2011086
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#65905}