sepolicy: minigbm_msm: fix vendor.minigbm.debug prop access denials am: 4746684811 am: e6ebfb6e97

Original change: https://android-review.googlesource.com/c/device/linaro/dragonboard/+/2752086

Change-Id: I99c2f302db003bbf2d5a1b65ac9137622ddefee8
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>