[U-Boot] MAINTAINERS: update maintained files for Rockchip

[Philipp Tomsich]

> With some of the recent cleanups (e.g. moving the DRAM controller
> drivers for Rockchip devices to drivers/ram/rockchip), the files
> and paths listed in MAINTAINERS no longer covered what really is
> looked after as part of the Rockchip port.
> 
> This commit updates the files/paths listed in MAINTAINERS for the
> Rockchip port.  I am certain, though, that this will have missed some
> additional paths that should have been included...
> 
> Signed-off-by: Philipp Tomsich <philipp.tomsich at theobroma-systems.com>
> Reviewed-by: Simon Glass <sjg at chromium.org>
> ---
> 
>  MAINTAINERS | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 

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