Since we only care about one bit in the lower 32 bits, we can always
perform smi checking while looking at the lower bits.

This improves pointer compression, since we wouldn't need to decompress,
while not affecting the non-pointer compression case.

Change-Id: Ic020fefcc92de0516148f34a3caacc60ff29556b
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1876050
Commit-Queue: Santiago Aboy Solanes <solanes@chromium.org>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#64593}