ARM: dts: rockchip: add pmic rk805 dt node for rv1108 evb

RK805 is used as the voltage regulator on rv1108 evaluation
board. Add device tree node for it.

Signed-off-by: Andy Yan <andy.yan@rock-chips.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>