[U-Boot] rockchip: rk322x: enable fastboot to set boot mode tag

[Philipp Tomsich]

> To support fastboot "fastboot reboot-bootloader" cmd.
> 
> Signed-off-by: Kever Yang <kever.yang at rock-chips.com>
> Reviewed-by: Simon Glass <sjg at chromium.org>
> ---
> 
>  arch/arm/mach-rockchip/rk322x-board.c | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
> 

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