Cleanup the audio mess

Change-Id: Ib1c91f13ebf8a5e4f89a9298e815f6a06e68fbd4
add AUDIO_LEGACY_HACK flag, reenable BOARD_HAVE_PRE_KITKAT_AUDIO_BLOB flag

Change-Id: I23f4fcc520cea1e7f16b07a779cbdbf18e32853d