arm: dts: i.mx8x: add #cooling-cells properties

Fix dtb building warnings:
Warning (cooling_device_property): /thermal-zones/cpu-thermal0/cooling-maps/map0:
Missing property '#cooling-cells' in node /cpus/cpu@0 or bad phandle (referred from cooling-device[0])

Signed-off-by: Anatolij Gustschin <agust@denx.de>
Reviewed-by: Stefano Babic <sbabic@denx.de>
Reviewed-by: Fabio Estevam <festevam@gmail.com>

arch/arm/dts/fsl-imx8-ca35.dtsi

@@ -18,6 +18,7 @@
 			reg = <0x0 0x0>;
 			enable-method = "psci";
 			next-level-cache = <&A35_L2>;
+			#cooling-cells = <2>;
 		};
 
 		A35_1: cpu@1 {
@@ -26,6 +27,7 @@
 			reg = <0x0 0x1>;
 			enable-method = "psci";
 			next-level-cache = <&A35_L2>;
+			#cooling-cells = <2>;
 		};
 
 		A35_2: cpu@2 {
@@ -34,6 +36,7 @@
 			reg = <0x0 0x2>;
 			enable-method = "psci";
 			next-level-cache = <&A35_L2>;
+			#cooling-cells = <2>;
 		};
 
 		A35_3: cpu@3 {
@@ -42,6 +45,7 @@
 			reg = <0x0 0x3>;
 			enable-method = "psci";
 			next-level-cache = <&A35_L2>;
+			#cooling-cells = <2>;
 		};
 
 		A35_L2: l2-cache0 {