arm64: dts: layerscape: remove cooling-max-state and cooling-min-state

Remove unused property cooling-max-state and cooling-min-state.
Remove undocument property #cooling-cells for ti,amc6821.
Fix below dtb_check warning:
arch/arm64/boot/dts/freescale/fsl-lx2160a-clearfog-cx.dtb: fan-temperature-ctrlr@18: '#cooling-cells', 'cooling-max-state', 'cooling-min-state' do not match any of the regexes: 'pinctrl-[0-9]+'
        from schema $id: http://devicetree.org/schemas/hwmon/ti,amc6821.yaml



Signed-off-by: Frank Li <Frank.Li@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>