minigbm: remove vgem backend

It's not used anymore, or atleast shouldn't be.

BUG=none
TEST=CQ will test

Change-Id: Ib9232a7704bd39e59a8e2a5bc2ece62c5dd8e9c1
Reviewed-on: https://chromium-review.googlesource.com/1643676
Tested-by: Gurchetan Singh <gurchetansingh@chromium.org>
Commit-Ready: ChromeOS CL Exonerator Bot <chromiumos-cl-exonerator@appspot.gserviceaccount.com>
Legacy-Commit-Queue: Commit Bot <commit-bot@chromium.org>
Reviewed-by: Stéphane Marchesin <marcheu@chromium.org>
3 files changed