After compression, the values should only be used for their lower 32-bits (W registers).
This removes unnecessary 'ubfx' zero-extends.

The size of the embedded builtins is reduced by 0.2%.
This improves the ARES-6 by ~1.0%.

Bug: v8:7703

Change-Id: Ib9bd771b51e85717f415a346b37428f8821bf278
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1751722Reviewed-by: Martyn Capewell <martyn.capewell@arm.com>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Reviewed-by: Santiago Aboy Solanes <solanes@chromium.org>
Commit-Queue: Santiago Aboy Solanes <solanes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#63196}