fix libmix encoder klockwork issues, rename IntelMetadatabuffer APIs

BZ: 50965

fix libmix encoder klockwork issues, remove all unused variables;
rename IntelMetadatabuffer APIs, rename SetBytes to UnSerialize,
GetBytes to Serialize, SetBytes/GetBytes will be dropped later;
Refine encoder code to avoid dynamic memory allocation.

Change-Id: I44344bb6d2e8536e65ecee8957e67722c1af21e5
Signed-off-by: Zhao Liang <leo.zhao@intel.com>
Reviewed-on: http://android.intel.com:8080/60688
Reviewed-by: Ding, Haitao <haitao.ding@intel.com>
Tested-by: Ding, Haitao <haitao.ding@intel.com>
Reviewed-by: buildbot <buildbot@intel.com>
Tested-by: buildbot <buildbot@intel.com>
8 files changed