[U-Boot] rockchip: rk3399: correct SPL_MAX_SIZE

[Philipp Tomsich]

On Wed, 14 Jun 2017, Kever Yang wrote:

> The SPL_MAX_SIZE is the internal memory size minux the space
> used by bootrom.
>
> Signed-off-by: Kever Yang <kever.yang at rock-chips.com>
> Reviewed-by: Philipp Tomsich <philipp.tomsich at theobroma-systems.com>
> Reviewed-by: Simon Glass <sjg at chromium.org>
> ---

Applied to u-boot-rockchip/master, thanks!