ARM: dts: rockchip: Use GPU as cooling device for the GPU thermal zone of the rk3288

Currently the CPUs are used as cooling devices of the rk3288 GPU
thermal zone. The CPUs are also configured as cooling devices in the
CPU thermal zone, which indirectly helps with cooling the GPU thermal
zone, since the CPU and GPU temperatures are correlated on the rk3288.

Configure the ARM Mali Midgard GPU as cooling device for the GPU
thermal zone instead of the CPUs.
Signed-off-by: NMatthias Kaehlcke <mka@chromium.org>
Reviewed-by: NDouglas Anderson <dianders@chromium.org>
Signed-off-by: NHeiko Stuebner <heiko@sntech.de>

arch/arm/boot/dts/rk3288.dtsi

@@ -552,10 +552,7 @@
 				map0 {
 					trip = <&gpu_alert0>;
 					cooling-device =
-						<&cpu0 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>,
-						<&cpu1 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>,
-						<&cpu2 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>,
-						<&cpu3 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>;
+						<&gpu THERMAL_NO_LIMIT THERMAL_NO_LIMIT>;
 				};
 			};
 		};