libmix: report missing reference frame in AVC decoder

BZ: 147912

1)record the reference frame missing in updateDPB.
2)change the variable name to keep coding style consistency.

Change-Id: Ib305e3cfe03a2f060e26730c8aab422d2e7afbae
Signed-off-by: Dan Liang <dan.liang@intel.com>
Signed-off-by: pingshix <pingx.shi@intel.com>
3 files changed