arm64: dts: rockchip: define vdd_log on rk3399-puma

vdd_log supplied a lot of the logic parts of the soc and is
supplied through pwm2.

Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Link: https://lore.kernel.org/r/20211227234529.1970281-1-heiko@sntech.de