The operator== in RegisterBase only compares the reg_code. On arm64 we have
another 'base', CPURegister. Before this change, registers from different
classes but with the same register number would compare as equal.
For example, x30 == d30 would be true, which is incorrect.

Change-Id: I8f19139df3f041b07bfa0883ec5ca768ef540802
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1745475Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Rodolph Perfetta <rodolph.perfetta@arm.com>
Cr-Commit-Position: refs/heads/master@{#63145}