[U-Boot] [U-Boot, 1/2] rockchip: rk3188: add support for usb-uart functionality

[Philipp Tomsich]

> Rockchip socs can route the debug uart pins through the d+ and d- pins
> of one specific usbphy per soc. Add a config option and implement the
> setting on the rk3188.
> 
> Signed-off-by: Heiko Stuebner <heiko at sntech.de>
> ---
>  .../include/asm/arch-rockchip/grf_rk3188.h    | 42 +++++++++++++++++++
>  arch/arm/mach-rockchip/Kconfig                |  8 ++++
>  arch/arm/mach-rockchip/rk3188-board-spl.c     | 27 ++++++++++--
>  3 files changed, 73 insertions(+), 4 deletions(-)
> 

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