[U-Boot] [U-Boot, 2/3] rockchip: doc: update U-Boot location info

[Philipp Tomsich]

> Update rockchip U-Boot location to 0x4000/16384.
> 
> Signed-off-by: Kever Yang <kever.yang at rock-chips.com>
> Acked-by: Philipp Tomsich <philipp.tomsich at theobroma-systems.com>
> ---
> 
>  doc/README.rockchip | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 

Reviewed-by: Philipp Tomsich <philipp.tomsich at theobroma-systems.com>