asahi: Add some magic IOGPU routines

asahi: Add some magic IOGPU routines

These turned out to be software defined structures consumed by the macOS
kernel (specifically, by IOGPUCommandQueue). I'm a bit bothered by the
sheer amount of random hex flying about, though Hector made some
progress on deciphering the structure. Nevertheless there's some comfort
knowing it's not actual hardware magic.

Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Acked-by: Jason Ekstrand <jason@jlekstrand.net>
Acked-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/10582>