minigbm: rockchip/mediatek: add PROTECTED flag back in

crrev.com/c/1643677 removed it, so we should add it back in.

BUG=b:141347335
TEST=GtsExoPlayerTestCases/GtsMediaTestCases

Change-Id: Ic49bd4158349da6170e8435c5c516954fe1646fa
Reviewed-on: https://chromium-review.googlesource.com/1821693
Tested-by: Gurchetan Singh <gurchetansingh@chromium.org>
Commit-Ready: Kazuhiro Inaba <kinaba@chromium.org>
Legacy-Commit-Queue: Commit Bot <commit-bot@chromium.org>
Reviewed-by: Gurchetan Singh <gurchetansingh@chromium.org>
2 files changed