Camera: Clarify SCALER_CROP_REGION usage am: d341edc3e7 am: 1a47fb441a am: 0ed134d9e3 am: 702bed508d

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

Change-Id: I15f6a4a0b3a2f787da1169a45a54543a79ac9808