[U-Boot] [U-Boot, v4] 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 environment variable which represents the reset reason.
> 
> Signed-off-by: Wadim Egorov <w.egorov at phytec.de>
> ---
> Changes in v4:
> - Factore out env_set()
> - Use BIT/GENMASK for CRU_GLB_RST_ST register enum
> ---
>  arch/arm/include/asm/arch-rockchip/cru_rk3288.h | 12 ++++++++
>  arch/arm/mach-rockchip/rk3288-board.c           | 39 +++++++++++++++++++++++++
>  2 files changed, 51 insertions(+)
> 

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