GPU/HW: Set max resolution scale to 32

The UI is intentionally left at 16x. Going too high **will** make you
run out VRAM and your system will start acting strangely. But for those
people who really want to do it, you can go 32x in Vulkan with the SDL
frontend, or by setting it in the ini.

src/core/gpu.h

@@ -43,7 +43,7 @@ public:
     MAX_FIFO_SIZE = 4096,
     DOT_TIMER_INDEX = 0,
     HBLANK_TIMER_INDEX = 1,
-    MAX_RESOLUTION_SCALE = 16,
+    MAX_RESOLUTION_SCALE = 32,
   };
 
   enum : u16