arm: dts: rockchip: move all rk3288 u-boot specific properties in separate dtsi files

In order to sync rk3288.dtsi from Linux it needed to
move all u-boot specific properties in separate dtsi files.

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