The decoder has the assumption that it always holds that pc <= end.
However, in the FunctionBodyDecoder, end was set to start to terminate
the decoding loop. Thereby the assumption was violated, which caused a
crash. I set end to pc now to end the decoding loop, which preserves
the assumption and terminates the loop.

BUG=chromium:709741
TEST=unittests/FunctionBodyDecoderTest.Regression709741
R=clemensh@chromium.org

Change-Id: I5bfd61bdc4809fc16f12ca8611876c66a79aaa36
Reviewed-on: https://chromium-review.googlesource.com/472723
Commit-Queue: Andreas Haas <ahaas@chromium.org>
Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#44524}