ARM: dts: rockchip: move the public part to rk3288-evb common

Rk3288-evb-act8846 and rk3288-evb-rk808 are the power boards of
rk3288-evb, they provide the same power supply interface to the
motherboard. Sort out them, put the public part to rk3288-evb.dtsi,
such as gmac and cpu-supply, leaving only the power section.

Signed-off-by: Chris Zhong <zyw@rock-chips.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>