MAINTAINERS: add rockchip regex for more files and directories

The current files and directories with wildcard patterns for
Rockchip patches in MAINTAINERS is not always complete.
Add the regex for DT related files and a generic regex for
catching some other forgotten cases, so that the maintainers
receive all Rockchip related patches.

Signed-off-by: Johan Jonker <jbx6244@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Jagan Teki <jagan@amarulasolutions.com>