board: rockchip: rk3308: Add device tree files and myself to MAINTAINERS

Update MAINTAINERS files for RK3308 boards to include related device
tree files. Also add myself as a reviewer for the ROCK Pi S board.

Signed-off-by: Jonas Karlman <jonas@kwiboo.se>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>
2 files changed