panfrost: Add pandecode support for Valhall (v9)

Add XML for the next major architecture version of Mali, v9, and add support for the new architecture to pandecode. I held off sending this merge request while reverse-engineering actively to avoid spamming mesa with commits discovering new unknown fields. That r/e cycle has settled down so I'd like to move forward with this... my branch adding Valhall support to Mesa is big enough as it is.