minigbm: add gbm_bo_get_fd_for_plane

One more piece in aligning with Mesa GBM ..

BUG=b:145747113
TEST=compile

Change-Id: Ic9d5dad5705feccd7005f40370f59d0339fe8bfc
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/minigbm/+/2803580
Reviewed-by: Gurchetan Singh <gurchetansingh@chromium.org>
Tested-by: Gurchetan Singh <gurchetansingh@chromium.org>
Commit-Queue: Gurchetan Singh <gurchetansingh@chromium.org>
3 files changed