[U-Boot] [PATCH 3/3] x86: Mention running U-Boot in 64-bit mode in the README

[Bin Meng]

On Sun, Jul 17, 2016 at 3:23 PM, Simon Glass <sjg at chromium.org> wrote:
> This feature is not supported. Document this, and add some details on how it
> might be implemented.
>
> Signed-off-by: Simon Glass <sjg at chromium.org>
> ---
>
>  doc/README.x86 | 18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)
>

Reviewed-by: Bin Meng <bmeng.cn at gmail.com>