Set the audio/video streams per sceMpegGet*Au().

This fixes #2226, thanks to @raven02 for finding the issue.  Could also
help e.g. Xyanide: Resurrection and a few other games.

The video codec change path is not super well tested, because I couldn't
find a game that triggered it, but it should work.
Merge pull request #4993 from unknownbrackets/mpeg-minor

Set the audio/video streams per sceMpegGet*Au()