Comparisons were allowing asm 'int' values in places
that require strict 'signed' or 'unsigned' but not both.

Fixes crash when these make it to asm-wasm.

BUG=599413
BUG=v8:4203
R=aseemgarg@chromium.org

Review-Url: https://codereview.chromium.org/2106683003
Cr-Commit-Position: refs/heads/master@{#37353}