minigbm: add helper function for detecting DRI devices

and discovering "default" device.

These are utility functions to help virglrenderer and possibly other clients
enumerate and discover DRI devices. They can be improved separately from
virglrenderer.

BUG=b:175246639
TEST=build and run together with virglrenderer change

Change-Id: I86c3e68cdab5a824184e744c4c90fb7daa316377
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/minigbm/+/2583188
Tested-by: Dominik Behr <dbehr@chromium.org>
Auto-Submit: Dominik Behr <dbehr@chromium.org>
Reviewed-by: Gurchetan Singh <gurchetansingh@chromium.org>
Commit-Queue: Dominik Behr <dbehr@chromium.org>
2 files changed