From: Jarod Wilson on
gitlab.com
https://gitlab.com/cki-project/kernel-ark/-/merge_requests/1815#note_9892...
I believe the old thinking was that then-always-pci-less s390x would never
need to build it (but I think some s390x variants have pci now?) and most
embedded arm64 systems had no pci as well. I suspect we could enable this
universally now, though I'm not sure if we want to turn on sienna for
previously unsupported arches? Baseline sfc blanket enablement can be done for
sure though.