Check for no audio more directly.

This fixes some cases where the flag was set wrong.
Trigger memchecks on writing out video data.
Trigger memchecks on audio decode from video.
Invalidate when writing video image.

It is required to update the framebuffer, of course.  Fixes Dead or Alive
video flicker.
Allow smaller psmfplayer buffer sizes.

Some libpsmfplayer.prx libraries allow smaller.
Don't return video/audio the first couple frames.

Fixes issues where games don't expect audio to be written to the display
buffer for the first couple games.  Reported to fix #5416.
Merge pull request #5977 from unknownbrackets/psmfplayer

Fix video flicker, add memchecks and detect no audio better