libmix: refine error report

BZ: 147912

The previous implementation  will count one less MB error.

Change-Id: I3a7b5a19282928dd0f70ae999bf13433d9ae79f7
Signed-off-by: Dan Liang <dan.liang@intel.com>
Signed-off-by: pingshix <pingx.shi@intel.com>
1 file changed