ARM: dts: rockchip: add core rk3288 dtsi

Node definitions shared by all rk3288 based boards.

Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Tested-by: Will Deacon <will.deacon@arm.com>
Tested-by: Doug Anderson <dianders@chromium.org>
Reviewed-by: Doug Anderson <dianders@chromium.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>