When loading the code object entry, we can do a little bit of strength
reduction to avoid a sign extend, `tst` and `lsl` instruction,
especially given Code::IsOffHeapTrampoline::kMask is a single-bit mask
we can use `tbz`.

Change-Id: I89fcd64cb517bf1ba8b43c05e9a784a9237889d8
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3168274Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Pierre Langlois <pierre.langlois@arm.com>
Cr-Commit-Position: refs/heads/main@{#76933}