arm64: dts: rockchip: Add support for two PWM fans on helios64

On the helios64 board the two connectors P6 and P7 are supposed to
power two fans. Add the corresponding pwm-fan devices.

Signed-off-by: Uwe Kleine-König <uwe@kleine-koenig.org>
Link: https://lore.kernel.org/r/20210510090607.970145-1-uwe@kleine-koenig.org


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