Vsync is messed up when using shaders

[xZabuzax]

Reported this issue here: https://github.com/hrydgard/ppsspp/issues/4440

Vsync is not working properly in the latest revisions when you use a shader, if Vsync and any shader are enabled Vsync won't work unless the emu is in windowed mode first and then you alt+enter to go to fullscreen.

To reproduce the issue:

Vsync and a shader is enabled and the emu is in fullscreen, when you play a game you will have screen tearing so to fix it you need to alt+enter to go to windowed mode and alt+enter again to go to fullscreen.

Another way to fix it is starting the game with no shaders and after the game is loaded you can enable the shader and you won't have screen tearing.