Vite: return system installed memory

src/cpuinfo/SDL_cpuinfo.c

@@ -1025,6 +1025,13 @@ SDL_GetSystemRAM(void)
             }
         }
 #endif
+#ifdef __VITA__
+        if (SDL_SystemRAM <= 0) {
+            /* Vita has 512MiB on SoC, that's split into 256MiB(+109MiB in extended memory mode) for app
+               +26MiB of physically continuous memory, +112MiB of CDRAM(VRAM) + system reserved memory. */
+            SDL_SystemRAM = 536870912;
+        }
+#endif
 #endif
     }
     return SDL_SystemRAM;