rockchip: cosmetic: Sort RK3288 boards

Sort rk3288 boards in alphabetical order.

Signed-off-by: Jernej Skrabec <jernej.skrabec@siol.net>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>
Reviewed-by: Eddie Cai <eddie.cai.linux@gmail.com>
Acked-by: Simon Glass <sjg@chromium.org>