Avoid unbinding the current fbo on block transfer.

Improves God of War performance by 25% (at least in the demo.)
Optimize the case of a direct byte copy.

Small improvement (like 3.5%) in God of War.
Interpret iForceMaxEmulatedFPS based on 1.001 NTSC.
Merge pull request #5877 from unknownbrackets/gpu-minor

Improve God of War performance