Fix RG350 video settings

1. Can't use HWSURFACE, as the code doesn't lock it.
   Double-buffering with HWSURFACE would be an alternative but the
   current game rendering code doesn't play well with it due to how it
   updates the UI
2. RG350 screen is RGB, not BGR (my microscope flipped the image),
   16-bit is the correct color depth.

CMake/rg350_defs.cmake

@@ -1,8 +1,7 @@
 set(sodium_USE_STATIC_LIBS ON)
 set(NONET ON)
 set(USE_SDL1 ON)
-set(SDL1_VIDEO_MODE_BPP 15) # BGR
-set(SDL1_VIDEO_MODE_FLAGS SDL_HWSURFACE)
+set(SDL1_VIDEO_MODE_BPP 16)
 set(PREFILL_PLAYER_NAME ON)
 set(JOY_AXIS_LEFTX 0)
 set(JOY_AXIS_LEFTY 1)