Upgrade libmpeg2 to v1.2.0 am: 38399a9b2f

Original change: https://android-review.googlesource.com/c/platform/external/libmpeg2/+/2698473

Change-Id: I0c4a04da651eda9fac4d4c0c7833e1c3ad72904b
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>