[U-Boot] rockchip: rk3288: Add reset reason detection

[Philipp Tomsich]

> Sometimes it's helpful to know the reset reason caused in the SoC.
> Add reset reason detection for the RK3288 SoC.
> This will set an environemt variable which represents the reset reason.
> 
> Signed-off-by: Wadim Egorov <w.egorov at phytec.de>
> ---
>  arch/arm/mach-rockchip/rk3288-board.c | 28 ++++++++++++++++++++++++++++
>  1 file changed, 28 insertions(+)
> 

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