Add /dev permissions to dynamic sensor README.md . am: 3493565708

Original change: https://googleplex-android-review.googlesource.com/c/platform/hardware/libhardware/+/17866052

Change-Id: Ied7f878e32da7e34df04675d7a1c5aa1d99fc2ab
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>