pixel-sepolicy: init_dpm.sh to read/write on custom_ab_block_device am: e682a521ee

Original change: https://googleplex-android-review.googlesource.com/c/platform/hardware/google/pixel-sepolicy/+/23469768

Change-Id: I70bc8cc1f73003a8a551dbd41986d8641a2e6cf8
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>