Fix buffer queue when filled in one shot.

It would mod by the size and think it was empty, even though it had plenty
of data.  This could happen if a game creates a ringbuffer with 512
packets and then does a single put operation with 512 packets.

Such behavior is rare though, since it will cause lag in starting the
video.
Reset "no audio data" flag when adding more data.

It might have audio data.  Although, probably, we should detect this when
sceMpegGetAtracAu() is called.
Merge pull request #5073 from unknownbrackets/mpeg-minor

Fix buffer queue when filled in one shot