board: google: veyron: add more DT files to MAINTAINERS

The Google Veyron rk3288 DT files are synced from Linux.
Add a maintainer to look after them and to help with
review and testing.

Signed-off-by: Johan Jonker <jbx6244@gmail.com>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>