riscos: Disable the mouse pointer for now

src/video/riscos/SDL_riscosmodes.c

@@ -305,7 +305,7 @@ RISCOS_SetDisplayMode(_THIS, SDL_VideoDisplay * display, SDL_DisplayMode * mode)
     }
 
     /* Turn the mouse pointer on */
-    _kernel_osbyte(106, 1, 0);
+    /* _kernel_osbyte(106, 1, 0); */
 
     return 0;
 }