panfrost: Move bifrost_lanes_per_warp to common

Whereas the compiler needs to know the warp size for lowering divergent
indirects, the driver needs to know it to report the subgroup size. Move the
Bifrost-specific helper to common and add the trivial implementation for
Midgard.

Signed-off-by: Alyssa Rosenzweig <alyssa@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/17265>
3 files changed