Also introduced a new generic macro to decode vx instructions.

Change-Id: I52477213555381b401022434de2946f91558a0b6
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2732609Reviewed-by: Junliang Yan <junyan@redhat.com>
Commit-Queue: Milad Fa <mfarazma@redhat.com>
Cr-Commit-Position: refs/heads/master@{#73174}