arm64: dts: rockchip: init rk3399 vop clock rates

We need to init vop aclk and hclk incase the U-Boot does not do
the initialize.

Signed-off-by: Kever Yang <kever.yang@rock-chips.com>
Reviewed-by: Mark Yao <mark.yao@rock-chips.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>