pan/bi: Rework Valhall register alignment

Because we lower SPLIT and COLLECT before RA, we need to consider offsets when
determining the dimensions of vectors, in order to align properly. Lowering
COLLECT post-RA would avoid this special case.

Signed-off-by: Alyssa Rosenzweig <alyssa@collabora.com>
Part-of: <!16780>
41 jobs for !16780 with bifrost/nodearray in 16 minutes and 18 seconds (queued for 3 seconds)
latest merge request