arm64: dts: rockchip: Add basic dts for RK3308 EVB

This board use uart4 as debug port and arm core voltage
is modulated by pwm, logic voltage is fixed to 1.05V.

Signed-off-by: Andy Yan <andy.yan@rock-chips.com>
Link: https://lore.kernel.org/r/20191021084657.28629-1-andy.yan@rock-chips.com


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