Pixelstats: support cca_rate sysfs am: e539aa7d02 am: 88dedddd8d

Original change: https://googleplex-android-review.googlesource.com/c/platform/hardware/google/pixel/+/20348458

Change-Id: Ifc4323319870a5a2c7f6fab74782a06ee2767329
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>