[U-Boot] [U-Boot, v3, 3/3] rockchip: check download key before bootup

[Philipp Tomsich]

> Enter download mode if the download key pressed.
> 
> Signed-off-by: Andy Yan <andy.yan at rock-chips.com>
> ---
> 
> Changes in v3: None
> Changes in v2:
> - more document
> - move adc key detect as the default
> 
>  arch/arm/mach-rockchip/boot_mode.c | 43 ++++++++++++++++++++++++++++++++++++++
>  1 file changed, 43 insertions(+)
> 

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