Revert "decoder: set u4_frame_decoded to true only after both fields are decoded" am: e0ad0016f0 am: 5ddd1567f9 am: a5a03d8967

Original change: https://googleplex-android-review.googlesource.com/c/platform/external/libavc/+/10959457

Change-Id: I8134fb8f88f51fb0a048503c06cea21f0cbadae3