doc: board: rockchip: Improve supported board list format

As an additional step to move documentation to doc/boards/rockchip
improve format of the supported board list to make it more readable.
Additionally, add the configuration files used to build them based on
doc/README.rockchip.

Signed-off-by: Walter Lozano <walter.lozano@collabora.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>
1 file changed