Revert "stagefright: Set bit_width if ENABLE_AV_ENHANCEMENTS is defined"

This reverts commit 5fc6701fe9af4bdd51e084554fa820f2734cdb12.
Revert "stagefright: Improve 24-bit support"

This reverts commit 405c6665b83e62898fe639c14cac76a521e769c4.