arm64: dts: rockchip: Remove #cooling-cells from fan on Theobroma lion

All Theobroma boards use a ti,amc6821 as fan controller.
It normally runs in an automatically controlled way and while it may be
possible to use it as part of a dt-based thermal management, this is
not yet specified in the binding, nor implemented in any kernel.

Newer boards already don't contain that #cooling-cells property, but
older ones do. So remove them for now, they can be re-added if thermal
integration gets implemented in the future.

There are two further occurences in v6.12-rc in px30-ringneck and
rk3399-puma, but those already get removed by the i2c-mux conversion
scheduled for 6.13 . As the undocumented property is in the kernel so
long, I opted for not causing extra merge conflicts between 6.12 and 6.13

Fixes: d99a02bcfa ("arm64: dts: rockchip: add RK3368-uQ7 (Lion) SoM")
Cc: Quentin Schulz <quentin.schulz@theobroma-systems.com>
Cc: Klaus Goger <klaus.goger@theobroma-systems.com>
Reviewed-by: Quentin Schulz <quentin.schulz@cherry.de>
Reviewed-by: Dragan Simic <dsimic@manjaro.org>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Link: https://lore.kernel.org/r/20241008203940.2573684-7-heiko@sntech.de
Signed-off-by: Heiko Stuebner <heiko@sntech.de>

arch/arm64/boot/dts/rockchip/rk3368-lion.dtsi

@@ -61,7 +61,6 @@
 			fan: fan@18 {
 				compatible = "ti,amc6821";
 				reg = <0x18>;
-				#cooling-cells = <2>;
 			};
 
 			rtc_twi: rtc@6f {