remove enum gbm_bo_format

remove enum gbm_bo_format

The presence of this enum makes mistakes handling gbm formats very easy
to make. With this patch, no new code can use this enum. Any old code
that tries will see errors.

BUG=None
TEST=drm-tests
CQ-DEPEND=CL:343592

Change-Id: If3b19975a137928965f14bad26d1e895dd839810
Reviewed-on: https://chromium-review.googlesource.com/343528
Commit-Ready: Zach Reizner <zachr@chromium.org>
Tested-by: Zach Reizner <zachr@chromium.org>
Reviewed-by: Stéphane Marchesin <marcheu@chromium.org>
Reviewed-by: Haixia Shi <hshi@chromium.org>