When we narrow a signed32 comparison to uint8 or uint16 representation,
we also need to change the condition to unsigned comparisons otherwise
the comparison will be done on int16/int8 which interprets the narrowed
bits wrong.

R=epertoso@chromium.org
BUG=v8:5254

Review-Url: https://codereview.chromium.org/2202803003
Cr-Commit-Position: refs/heads/master@{#38231}