radv/rra: Refactor validation
Here are the promised validation cleanups. The output looks like this now:
radv: rra: Validation failed at header:
Invalid BVH offset 1800973
Too many instances
radv: rra: Validation failed at internal node (offset=64):
Invalid child offset (child index 0)
Invalid child offset (child index 1)
Invalid child offset (child index 2)
Invalid child offset (child index 3)