arm64: dts: rockchip: Fix NanoPC-T4 cooling maps

Although it appeared to follow logically from the bindings, apparently
the thermal framework can't properly cope with a single cooling device
being shared between multiple maps. The CPU zone is probably easier to
overheat, so remove the references to the (optional) fan from the GPU
cooling zone to avoid things getting confused. Hopefully GPU-intensive
tasks will leak enough heat across to the CPU zone to still hit the
fan trips before reaching critical GPU temperatures.

Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/5bb39f3115df1a487d717d3ae87e523b03749379.1573908197.git.robin.murphy@arm.com


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