MediaFormat: fix key value for KEY_MAX_OUTPUT_CHANNEL_COUNT am: a991d6bdc2 am: 42bf4dc517

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/16118478

Change-Id: I3ae18c87b8db42e5cd8442d17eef7c5baff874d8