minigbm: i915: use protected content feature

minigbm: i915: use protected content feature

This enables protected content playback on gen 12 and greater
i915.

BUG=b:153111783,b:155511259
TEST=Protected playback works w/ associated Chrome OS changes

Change-Id: I829dddf506b3b765e5d2f25f2b77af9ecc4f7309
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/minigbm/+/2459532
Reviewed-by: Jeffrey Kardatzke <jkardatzke@google.com>
Reviewed-by: Gurchetan Singh <gurchetansingh@chromium.org>
Tested-by: Jeffrey Kardatzke <jkardatzke@google.com>
Commit-Queue: Gurchetan Singh <gurchetansingh@chromium.org>