Try to improve FBO sizing

This is a conservative (and slightly hacky) fix for #4325 (Wild Arms XF).  It also fixes the same issue in Tales of Phantasia X (which is not always reachable, it depends on how you access the area and what framebuffers were created beforehand - but it's easy to reproduce in the demo.)

I don't really have the games with the primary issues here, but I checked shadows in Kingdom Hearts and videos in Star Ocean and there weren't any issues.  Tales of Destiny 2, which was involved in the original embiggening attempts, also seems fine.

-[Unknown]