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

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

Change-Id: I0f15d19e69098b725164dadcb046d53106228631
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>