arm64: dts: rockchip: Add dynamic-power-coefficient to rk3399 GPU

[LZhaoM]

arm64: dts: rockchip: Add dynamic-power-coefficient to rk3399 GPU

On a Radxa Rock 4B+ board, when executing the following stress test
command for a few hours:
glmark2-es2 -b refract:duration=60 -s 3840x2160 --off-screen --run-forever

The SoC temperature will increase gradually until it reaches the
critical temperature and triggers shutdown.
Kernel log:
kernel: thermal thermal_zone1: gpu-thermal: critical temperature reached, shutting down
kernel: reboot: HARDWARE PROTECTION shutdown (Temperature too high)

The reason is that the device tree gpu node does not provide a
dynamic-power-coefficient; without this value, the gpu cooling device is
not registered[0][1], so it will reach the critical temperature.

The value 2640 is based on this upstream patch:
https://lore.kernel.org/all/20231127081511.1911706-1-lukasz.luba@arm.com

[0]: https://github.com/radxa/kernel/blob/8582469f117fdfd5d1ab88fa7e4e15c3b714bf24/drivers/thermal/devfreq_cooling.c#L484-L489
[1]: https://github.com/radxa/kernel/blob/8582469f117fdfd5d1ab88fa7e4e15c3b714bf24/drivers/opp/of.c#L1594-L1606

[RadxaYuntian]

上游来的改动还是一般尽量cherrypick过来，保留原始提交信息