Bug fix:  error-concealment enabled changed postproc output

When error concealment is enabled, it swaps the mi and prev_mi ptrs after
each frame is decoded.  The postproc uses the mi ptr for the mode info context.
Now the postproc will use the correct mode info context.

Change-Id: I537ae5450f319c624999b44525bb52bb30047b7b
5 files changed