Camera: Clarify SCALER_CROP_REGION usage am: d341edc3e7 am: 7057ee2522 am: 346f77e532

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/av/+/12586223

Change-Id: I840512493bba3149ba21aeccd2fc8b54689aac71