Merge "document that media_codecs_sw.xml is part of mainline" am: b383ac72...

Merge "document that media_codecs_sw.xml is part of mainline" am: b383ac72 am: 7c9d6f97 am: 20770654

Original change: https://android-review.googlesource.com/c/platform/frameworks/av/+/2247581



Change-Id: I016571f172844c4c30d41fb54a399cd5e58e43e7
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>