ARM: dts: rockchip: add gpu nodes on rk3066/rk3188

The old Cortex-A9 socs use Mali400 GPUs with 4 pixel processors.
This adds the core gpu nodes with the per-soc interrupts but sharing
the core node.

Rockchip SoCs use only one clock to supply the GPUs

Signed-off-by: Heiko Stuebner <heiko@sntech.de>