[GTA VCS PPSSPP] Add ability to set arbitary FPS Limit instead of either 30 or 60 FPS.

[AnonPol]

I think the game would be less broken if the FPS was capped at 40-45 FPS rather than 60. Its mostly fine at 60 FPS but I notice some oddities here and there and I prefer to not play the game at 30 FPS to avoid those bugs. For Steam Deck users like me it would be ideal as I can set the refresh rate to match the 40-45 FPS Limit and not have any issues as a result.